       FreeBSD Documentation Project Primer for New Contributors

  The FreeBSD Documentation Project

   Copyright (c) 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005,
   2006, 2007, 2008, 2009 DocEng

   Thank you for becoming a part of the FreeBSD Documentation
   Project. Your contribution is extremely valuable.

   This primer covers everything you will need to know in order to
   start contributing to the FreeBSD Documentation Project, from the
   tools and software you will be using (both mandatory and
   recommended) to the philosophy behind the Documentation Project.

   This document is a work in progress, and is not complete. Sections
   that are known to be incomplete are indicated with a * in their
   name.

   Redistribution and use in source (XML DocBook) and 'compiled'
   forms (XML, HTML, PDF, PostScript, RTF and so forth) with or
   without modification, are permitted provided that the following
   conditions are met:

    1. Redistributions of source code (XML DocBook) must retain the
       above copyright notice, this list of conditions and the
       following disclaimer as the first lines of this file
       unmodified.

    2. Redistributions in compiled form (transformed to other DTDs,
       converted to PDF, PostScript, RTF and other formats) must
       reproduce the above copyright notice, this list of conditions
       and the following disclaimer in the documentation and/or other
       materials provided with the distribution.

     Important: THIS DOCUMENTATION IS PROVIDED BY THE FREEBSD
     DOCUMENTATION PROJECT "AS IS" AND ANY EXPRESS OR IMPLIED
     WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
     WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FREEBSD
     DOCUMENTATION PROJECT BE LIABLE FOR ANY DIRECT, INDIRECT,
     INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
     (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
     WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
     NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
     THIS DOCUMENTATION, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
     DAMAGE.

     --------------------------------------------------------------

   Table of Contents

   Preface

                Shell Prompts

                Typographic Conventions

                Notes, Tips, Important Information, Warnings, and
                Examples

                Acknowledgments

   1 Overview

                1.1 The FreeBSD Documentation Set

                1.2 Before You Start

                1.3 Quick Start

   2 Tools

                2.1 Mandatory Tools

                             2.1.1 Software

                             2.1.2 DTDs and Entities

                             2.1.3 Stylesheets

                2.2 Optional Tools

                             2.2.1 Software

   3 XML Primer

                3.1 Overview

                3.2 Elements, Tags, and Attributes

                             3.2.1 For You to Do...

                3.3 The DOCTYPE Declaration

                             3.3.1 Formal Public Identifiers (FPIs)

                             3.3.2 Alternatives to FPIs

                3.4 Escaping Back to SGML

                3.5 Comments

                             3.5.1 For You to Do...

                3.6 Entities

                             3.6.1 General Entities

                             3.6.2 Parameter Entities

                             3.6.3 For You to Do...

                3.7 Using Entities to Include Files

                             3.7.1 Using General Entities to Include
                             Files

                             3.7.2 Using Parameter Entities to
                             Include Files

                             3.7.3 For You to Do...

                3.8 Marked Sections

                             3.8.1 Marked Section Keywords

                             3.8.2 For You to Do...

                3.9 Conclusion

   4 XML Markup

                4.1 XHTML

                             4.1.1 Formal Public Identifier (FPI)

                             4.1.2 Sectional Elements

                             4.1.3 Block Elements

                             4.1.4 In-line Elements

                             4.1.5 Links

                4.2 DocBook

                             4.2.1 FreeBSD Extensions

                             4.2.2 Formal Public Identifier (FPI)

                             4.2.3 Document Structure

                             4.2.4 Block Elements

                             4.2.5 In-line Elements

                             4.2.6 Images

                             4.2.7 Links

   5 * Stylesheets

                5.1 * DSSSL

                5.2 CSS

                             5.2.1 The DocBook Documents

   6 Structuring Documents Under doc/

                6.1 The Top Level, doc/

                6.2 The lang.encoding/ Directories

                6.3 Document Specific Information

                             6.3.1 The Handbook

   7 The Documentation Build Process

                7.1 The FreeBSD Documentation Build Toolset

                7.2 Understanding Makefiles in the Documentation Tree

                             7.2.1 Subdirectory Makefiles

                             7.2.2 Documentation Makefiles

                7.3 FreeBSD Documentation Project Make Includes

                             7.3.1 doc.project.mk

                             7.3.2 doc.subdir.mk

   8 The Website

                8.1 Preparation

                             8.1.1 Using svn

                8.2 Build the Web Pages from Scratch

                8.3 Install the Web Pages into Your Web Server

                8.4 Environment Variables

   9 Translations

   10 Writing Style

                10.1 Style Guide

                             10.1.1 Letter Case

                             10.1.2 Acronyms

                             10.1.3 Indentation

                             10.1.4 Tag Style

                             10.1.5 White Space Changes

                             10.1.6 Non-Breaking Space

                10.2 Word List

   11 Using sgml-mode with Emacs

   12 See Also

                12.1 The FreeBSD Documentation Project

                12.2 XML

                12.3 HTML

                12.4 DocBook

                12.5 The Linux Documentation Project

   A. Examples

                A.1 DocBook <book>

                A.2 DocBook <article>

                A.3 Producing Formatted Output

                             A.3.1 Using Jade

   List of Examples

   1. A Sample Example

   3-1. Using an Element (Start and End Tags)

   3-2. Using an Element (Without Content)

   3-3. Elements within Elements; <em>

   3-4. Using An Element with An Attribute

   3-5. Single Quotes Around Attributes

   3-6. .profile, for sh(1) and bash(1) Users

   3-7. .cshrc, for csh(1) and tcsh(1) Users

   3-8. XML Generic Comment

   3-9. Erroneous XML Comments

   3-10. Defining General Entities

   3-11. Defining Parameter Entities

   3-12. Using General Entities to Include Files

   3-13. Using Parameter Entities to Include Files

   3-14. Structure of A Marked Section

   3-15. Using a CDATA Marked Section

   3-16. Using INCLUDE and IGNORE in Marked Sections

   3-17. Using A Parameter Entity to Control a Marked Section

   4-1. Normal XHTML Document Structure

   4-2. <h1>, <h2>, and Other Header Tags

   4-3. Bad Ordering of <hn> Elements

   4-4. <p>

   4-5. <blockquote>

   4-6. <ul> and <ol>

   4-7. Definition Lists with <dl>

   4-8. <pre>

   4-9. Simple Use of <table>

   4-10. Using rowspan

   4-11. Using colspan

   4-12. Using rowspan and colspan Together

   4-13. <em> and <strong>

   4-14. <tt>

   4-15. Using <a href="...">

   4-16. Using <a id="...">

   4-17. Linking to a Named Part of Another Document

   4-18. Linking to a Named Part of the Same Document

   4-19. Boilerplate <book> with <bookinfo>

   4-20. Boilerplate <article> with <articleinfo>

   4-21. A Simple Chapter

   4-22. Empty Chapters

   4-23. Sections in Chapters

   4-24. <para>

   4-25. <blockquote>

   4-26. <warning>

   4-27. <itemizedlist>, <orderedlist>, and <procedure>

   4-28. <programlisting>

   4-29. <co> and <calloutlist>

   4-30. <informaltable>

   4-31. Tables Where frame="none"

   4-32. <screen>, <prompt>, and <userinput>

   4-33. <emphasis>

   4-34. Quotations

   4-35. Keys, Mouse Buttons, and Combinations

   4-36. Applications, Commands, and Options

   4-37. <filename>

   4-38. <filename> Tag with package Role

   4-39. <devicename>

   4-40. <hostid> and Roles

   4-41. <username>

   4-42. <maketarget> and <makevar>

   4-43. <literal>

   4-44. <replaceable>

   4-45. <errorname>

   4-46. Attribute id on Chapters and Sections

   4-47. <anchor>

   4-48. Using <xref>

   4-49. Using <link>

   4-50. <ulink>

   A-1. DocBook <book>

   A-2. DocBook <article>

   A-3. Converting DocBook to HTML (One Large File)

   A-4. Converting DocBook to HTML (Several Small Files)

   A-5. Converting DocBook to Postscript

   A-6. Converting DocBook to PDF

     --------------------------------------------------------------

                                Preface

Shell Prompts

   The following table shows the default system prompt and superuser
   prompt. The examples will use this prompt to indicate which user
   you should be running the example as.

                  User                             Prompt             
   Normal user                         %                              
   root                                #                              

     --------------------------------------------------------------

Typographic Conventions

   The following table describes the typographic conventions used in
   this book.

                 Meaning                          Examples            
   The names of commands.               Use ls -l to list all files.  
   The names of files.                  Edit .login.                  
   On screen computer output.           You have mail.                
   What you type, when contrasted with  % su                          
   on-screen computer output.           Password:                     
   Manual page references.              Use su(1) to change user      
                                        names.                        
   User and group names                 Only root can do this.        
   Emphasis                             You must do this.             
   Command line variables; replace with To delete a file, type rm     
   the real name or variable.           filename                      
   Environment variables                $HOME is your home directory. 

     --------------------------------------------------------------

Notes, Tips, Important Information, Warnings, and Examples

   Within the text appear notes, warnings, and examples.

     Note: Notes are represented like this, and contain information
     that you should take note of, as it may affect what you do.

     Tip: Tips are represented like this, and contain information
     that you might find useful, or lead to an easier way to do
     something.

     Important: Important information is represented like this.
     Typically they flag extra steps you may need to carry out.

     Warning: Warnings are represented like this, and contain
     information warning you about possible damage if you do not
     follow the instructions. This damage may be physical, to your
     hardware or to you, or it may be non-physical, such as the
     inadvertent deletion of important files.

   Example 1. A Sample Example

   Examples are represented like this, and typically contain examples
   you should walk through, or show you what the results of a
   particular action should be.

     --------------------------------------------------------------

Acknowledgments

   My thanks to Sue Blake, Patrick Durusau, Jon Hamilton, Peter
   Flynn, and Christopher Maden, who took the time to read early
   drafts of this document and offer many valuable comments and
   criticisms.

     --------------------------------------------------------------

                           Chapter 1 Overview

   Welcome to the FreeBSD Documentation Project. Good quality
   documentation is very important to the success of FreeBSD, and the
   FreeBSD Documentation Project (FDP) is how a lot of that
   documentation is produced. Your contributions are very valuable.

   This document's main purpose is to clearly explain how the FDP is
   organized, how to write and submit documentation to the FDP, and
   how to effectively use the tools available to you when writing
   documentation.

   Everyone is welcome to join the FDP. There is no minimum
   membership requirement, no quota of documentation you need to
   produce per month. All you need to do is subscribe to the FreeBSD
   documentation project mailing list.

   After you have finished reading this document you should:

     * Know which documentation is maintained by the FDP.

     * Be able to read and understand the XML source code for the
       documentation maintained by the FDP.

     * Be able to make changes to the documentation.

     * Be able to submit your changes back for review and eventual
       inclusion in the FreeBSD documentation.

     --------------------------------------------------------------

1.1 The FreeBSD Documentation Set

   The FDP is responsible for four categories of FreeBSD
   documentation.

   Manual pages

           The English language system manual pages are not written
           by the FDP, as they are part of the base system. However,
           the FDP can (and has) re-worded parts of existing manual
           pages to make them clearer, or to correct inaccuracies.

           The translation teams are responsible for translating the
           system manual pages into different languages. These
           translations are kept within the FDP.

   FAQ

           The FAQ aims to address (in short question and answer
           format) questions that are asked, or should be asked, on
           the various mailing lists and newsgroups devoted to
           FreeBSD. The format does not permit long and comprehensive
           answers.

   Handbook

           The Handbook aims to be the comprehensive on-line resource
           and reference for FreeBSD users.

   Web site

           This is the main FreeBSD presence on the World Wide Web,
           visible at http://www.FreeBSD.org/ and many mirrors around
           the world. The web site is many people's first exposure to
           FreeBSD.

   The documentation for the web site, FreeBSD Handbook, and FAQ are
   available in the doc/ Subversion repository, which is located at
   https://svn.FreeBSD.org/doc/.

   Manual pages are available in the src/ Subversion repository,
   which is available at https://svn.FreeBSD.org/base/.

   This means that the logs of changes to these files are visible to
   anyone, and anyone can use svn to view the changes.

   In addition, many people have written tutorials or other web sites
   relating to FreeBSD. Some of these are stored in the Subversion
   repository as well (where the author has agreed to this). In other
   cases the author has decided to keep his documentation separate
   from the main FreeBSD repository. The FDP endeavors to provide
   links to as much of this documentation as possible.

     --------------------------------------------------------------

1.2 Before You Start

   This document assumes that you already know:

     * How to maintain an up-to-date local copy of the FreeBSD
       documentation by maintaining a local copy of the FreeBSD
       Subversion repository using svn.

     * How to download and install new software using either the
       FreeBSD Ports system or pkg_add(1).

     --------------------------------------------------------------

1.3 Quick Start

   If you just want to get going, and feel confident you can pick
   things up as you go along, follow these instructions.

    1. Install the textproc/docproj meta-port.

 # cd /usr/ports/textproc/docproj
 # make JADETEX=no install

    2. Get a local copy of the FreeBSD doc tree using svn.

       If network bandwidth or local drive space is a concern, then
       at minimum, the head/share and head/language/share directories
       will need to be checked out. For example:

 % mkdir -p head/share
 % mkdir -p head/en_US.ISO8859-1/share
 % svn checkout https://svn0.us-east.FreeBSD.org/doc/head/share head/share
 % svn checkout https://svn0.us-east.FreeBSD.org/doc/head/en_US.ISO8859-1/share head/en_US.ISO8859-1/share

       If you have plenty of disk space then you could check out
       everything.

 % svn checkout https://svn0.us-east.FreeBSD.org/doc/head head

         Note: svn0.us-east.FreeBSD.org is a public SVN server.
         Select the closest mirror and verify the mirror server
         certificate from the list of Subversion mirror sites.

    3. If you are preparing a change to an existing book or article,
       check it out of the repository as necessary. If you are
       planning on contributing a new book or article then use an
       existing one as a guide.

       For example, if you want to contribute a new article about
       setting up a VPN between FreeBSD and Windows 2000 you might do
       the following.

         1. Check out the articles directory.

 % svn checkout https://svn0.us-east.FreeBSD.org/doc/head/en_US.ISO8859-1/articles

         2. Copy an existing article to use as a template. In this
            case, you have decided that your new article belongs in a
            directory called vpn-w2k.

 % cd head/en_US.ISO8859-1/articles
 % svn export committers-guide vpn-w2k

       If you wanted to edit an existing document, such as the FAQ,
       which is in head/en_US.ISO8859-1/books/faq you would check it
       out of the repository like this.

 % svn checkout https://svn0.us-east.FreeBSD.org/doc/head/en_US.ISO8859-1/books/faq

    4. Edit the .xml files using your editor of choice.

    5. Test the markup using the lint target. This will quickly find
       any errors in the document without actually performing the
       time-consuming transformation.

 % make lint

       When you are ready to actually build the document, you may
       specify a single format or a list of formats in the FORMATS
       variable. Currently, html, html-split, txt, ps, pdf, and rtf
       are supported. The most up to date list of supported formats
       is listed at the top of the head/share/mk/doc.docbook.mk file.
       Make sure to use quotes around the list of formats when you
       build more than one format with a single command.

       For example, to convert the document to html only, you would
       use:

 % make FORMATS=html

       But when you want to convert the document to both html and txt
       format, you could use either two separate make(1) runs, with:

 % make FORMATS=html
 % make FORMATS=txt

       or, you can do it in one command:

 % make FORMATS="html txt"

    6. Submit your changes using send-pr(1).

     --------------------------------------------------------------

                            Chapter 2 Tools

   The FDP uses a number of different software tools to help manage
   the FreeBSD documentation, convert it to different output formats,
   and so on. You will need to use these tools yourself if you are to
   work with the FreeBSD documentation.

   All these tools are available as FreeBSD Ports and Packages,
   greatly simplifying the work you have to do to install them.

   You will need to install these tools before you work through any
   of the examples in later chapters. The actual usage of these tools
   is covered in later chapters.

     Use textproc/docproj If Possible: You can save yourself a lot of
     time if you install the textproc/docproj port. This is a
     meta-port which does not contain any software itself. Instead,
     it depends on various other ports being installed correctly.
     Installing this port should automatically download and install
     all of the packages listed in this chapter that you need.

     One of the packages that you might need is the JadeTeX macro
     set. In turn, this macro set requires TeX to be installed. TeX
     is a large package, and you only need it if you want to produce
     Postscript or PDF output.

     To save yourself time and space you must specify whether or not
     you want JadeTeX (and therefore TeX) installed when you install
     this port. Either do:

 # make JADETEX=yes install

     or

 # make JADETEX=no install

     as necessary. Alternatively you may install
     textproc/docproj-jadetex or textproc/docproj-nojadetex. These
     slave ports define the JADETEX variable for you, therefore they
     will install the same suite of applications on your machine.
     Note that you can produce only XHTML or ASCII text output if you
     do not install JadeTeX. PostScript or PDF output requires TeX.

     --------------------------------------------------------------

2.1 Mandatory Tools

  2.1.1 Software

   These programs are required before you can usefully work with the
   FreeBSD documentation, and they will allow you to convert the
   documentation to XHTML, plain text, and RTF formats. They are all
   included in textproc/docproj.

   Jade (textproc/jade)

           A DSSSL implementation. Used for converting marked up
           documents to other formats, including HTML and TeX.

   Tidy (www/tidy)

           An (X)HTML "pretty printer", used to reformat some of the
           automatically generated pages so that it is easier to
           follow.

   Links (www/links)

           A text-mode WWW browser that can also convert XHTML files
           to plain text.

   peps (graphics/peps)

           Some of the documentation includes images, some of which
           are stored as EPS files. These must be converted to PNG
           before most web browsers will display them.

     --------------------------------------------------------------

  2.1.2 DTDs and Entities

   These are the DTDs and entity sets used by the FDP. They need to
   be installed before you can work with any of the documentation.

   XHTML DTD (textproc/xhtml)

           XHTML is the markup language of choice for the World Wide
           Web, and is used throughout the FreeBSD web site.

   DocBook DTD (textproc/docbook)

           DocBook is designed for marking up technical
           documentation. All the FreeBSD documentation is written in
           DocBook.

   ISO 8879 entities (textproc/iso8879)

           19 of the ISO 8879:1986 character entity sets used by many
           DTDs. Includes named mathematical symbols, additional
           characters in the Latin character set (accents,
           diacriticals, and so on), and Greek symbols.

     --------------------------------------------------------------

  2.1.3 Stylesheets

   The stylesheets are used when converting and formatting the
   documentation for display on screen, printing, and so on.

   Modular DocBook Stylesheets (textproc/dsssl-docbook-modular)

           The Modular DocBook Stylesheets are used when converting
           documentation marked up in DocBook to other formats, such
           as HTML or RTF.

     --------------------------------------------------------------

2.2 Optional Tools

   You do not need to have any of the following installed. However,
   you may find it easier to work with the documentation if you do,
   and they may give you more flexibility in the output formats that
   can be generated.

     --------------------------------------------------------------

  2.2.1 Software

   JadeTeX and teTeX (print/jadetex and print/teTeX)

           Jade and teTeX are used to convert DocBook documents to
           DVI, Postscript, and PDF formats. The JadeTeX macros are
           needed in order to do this.

           If you do not intend to convert your documentation to one
           of these formats (i.e., HTML, plain text, and RTF are
           sufficient) then you do not need to install JadeTeX and
           teTeX. This can be a significant space and time saver, as
           teTeX is over 30MB in size.

             Important: If you decide to install JadeTeX and teTeX
             then you will need to configure teTeX after JadeTeX has
             been installed. print/jadetex/pkg-message contains
             detailed instructions explaining what you need to do.

   Emacs or XEmacs (editors/emacs or editors/xemacs)

           Both these editors include a special mode for editing
           documents marked up according to an SGML DTD. This mode
           includes commands to reduce the amount of typing you need,
           and help reduce the possibility of errors.

           You do not need to use them; any text editor can be used
           to edit marked up documents. You may find they make you
           more efficient.

   If anyone has recommendations for other software that is useful
   when manipulating XML documents, please let Documentation
   Engineering Team <doceng@FreeBSD.org> know, so they can be added
   to this list.

     --------------------------------------------------------------

                          Chapter 3 XML Primer

   The majority of FDP documentation is written in applications of
   XML. This chapter explains exactly what that means, how to read
   and understand the source to the documentation, and the sort of
   XML tricks you will see used in the documentation.

   Portions of this section were inspired by Mark Galassi's Get Going
   With DocBook.

     --------------------------------------------------------------

3.1 Overview

   Way back when, electronic text was simple to deal with.
   Admittedly, you had to know which character set your document was
   written in (ASCII, EBCDIC, or one of a number of others) but that
   was about it. Text was text, and what you saw really was what you
   got. No frills, no formatting, no intelligence.

   Inevitably, this was not enough. Once you have text in a
   machine-usable format, you expect machines to be able to use it
   and manipulate it intelligently. You would like to indicate that
   certain phrases should be emphasized, or added to a glossary, or
   be hyperlinks. You might want filenames to be shown in a
   "typewriter" style font for viewing on screen, but as "italics"
   when printed, or any of a myriad of other options for
   presentation.

   It was once hoped that Artificial Intelligence (AI) would make
   this easy. Your computer would read in the document and
   automatically identify key phrases, filenames, text that the
   reader should type in, examples, and more. Unfortunately, real
   life has not happened quite like that, and our computers require
   some assistance before they can meaningfully process our text.

   More precisely, they need help identifying what is what. Let's
   look at this text:

     To remove /tmp/foo use rm(1).

 % rm /tmp/foo

   It is easy to see which parts are filenames, which are commands to
   be typed in, which parts are references to manual pages, and so
   on. But the computer processing the document cannot. For this we
   need markup.

   "Markup" is commonly used to describe "adding value" or
   "increasing cost". The term takes on both these meanings when
   applied to text. Markup is additional text included in the
   document, distinguished from the document's content in some way,
   so that programs that process the document can read the markup and
   use it when making decisions about the document. Editors can hide
   the markup from the user, so the user is not distracted by it.

   The extra information stored in the markup adds value to the
   document. Adding the markup to the document must typically be done
   by a person-after all, if computers could recognize the text
   sufficiently well to add the markup then there would be no need to
   add it in the first place. This increases the cost (i.e., the
   effort required) to create the document.

   The previous example is actually represented in this document like
   this:

 <para>To remove <filename>/tmp/foo</filename> use &man.rm.1;.</para>

 <screen>&prompt.user; <userinput>rm /tmp/foo</userinput></screen>

   As you can see, the markup is clearly separate from the content.

   Obviously, if you are going to use markup you need to define what
   your markup means, and how it should be interpreted. You will need
   a markup language that you can follow when marking up your
   documents.

   Of course, one markup language might not be enough. A markup
   language for technical documentation has very different
   requirements than a markup language that was to be used for
   cookery recipes. This, in turn, would be very different from a
   markup language used to describe poetry. What you really need is a
   first language that you use to write these other markup languages.
   A meta markup language.

   This is exactly what the eXtensible Markup Language (XML) is. Many
   markup languages have been written in XML, including the two most
   used by the FDP, XHTML and DocBook.

   Each language definition is more properly called a grammar,
   vocabulary, schema or Document Type Definition (DTD). There are
   various languages to specify an XML grammar, for example, DTD
   (yes, it also means the specification language itself), XML Schema
   (XSD) or RELANG NG. The schema specifies the name of the elements
   that can be used, what order they appear in (and whether some
   markup can be used inside other markup) and related information.

   A schema is a complete specification of all the elements that are
   allowed to appear, the order in which they should appear, which
   elements are mandatory, which are optional, and so forth. This
   makes it possible to write an XML parser which reads in both the
   schema and a document which claims to conform to the schema. The
   parser can then confirm whether or not all the elements required
   by the vocabulary are in the document in the right order, and
   whether there are any errors in the markup. This is normally
   referred to as "validating the document".

     Note: This processing simply confirms that the choice of
     elements, their ordering, and so on, conforms to that listed in
     the grammar. It does not check that you have used appropriate
     markup for the content. If you tried to mark up all the
     filenames in your document as function names, the parser would
     not flag this as an error (assuming, of course, that your schema
     defines elements for filenames and functions, and that they are
     allowed to appear in the same place).

   It is likely that most of your contributions to the Documentation
   Project will consist of content marked up in either XHTML or
   DocBook, rather than alterations to the schemas. For this reason
   this book will not touch on how to write a vocabulary.

     --------------------------------------------------------------

3.2 Elements, Tags, and Attributes

   All the vocabularies written in XML share certain characteristics.
   This is hardly surprising, as the philosophy behind XML will
   inevitably show through. One of the most obvious manifestations of
   this philosophy is that of content and elements.

   Your documentation (whether it is a single web page, or a lengthy
   book) is considered to consist of content. This content is then
   divided (and further subdivided) into elements. The purpose of
   adding markup is to name and identify the boundaries of these
   elements for further processing.

   For example, consider a typical book. At the very top level, the
   book is itself an element. This "book" element obviously contains
   chapters, which can be considered to be elements in their own
   right. Each chapter will contain more elements, such as
   paragraphs, quotations, and footnotes. Each paragraph might
   contain further elements, identifying content that was direct
   speech, or the name of a character in the story.

   You might like to think of this as "chunking" content. At the very
   top level you have one chunk, the book. Look a little deeper, and
   you have more chunks, the individual chapters. These are chunked
   further into paragraphs, footnotes, character names, and so on.

   Notice how you can make this differentiation between different
   elements of the content without resorting to any XML terms. It
   really is surprisingly straightforward. You could do this with a
   highlighter pen and a printout of the book, using different colors
   to indicate different chunks of content.

   Of course, we do not have an electronic highlighter pen, so we
   need some other way of indicating which element each piece of
   content belongs to. In languages written in XML (XHTML, DocBook,
   et al) this is done by means of tags.

   A tag is used to identify where a particular element starts, and
   where the element ends. The tag is not part of the element itself.
   Because each grammar was normally written to mark up specific
   types of information, each one will recognize different elements,
   and will therefore have different names for the tags.

   For an element called element-name the start tag will normally
   look like <element-name>. The corresponding closing tag for this
   element is </element-name>.

   Example 3-1. Using an Element (Start and End Tags)

   XHTML has an element for indicating that the content enclosed by
   the element is a paragraph, called <p>.

 <p>This is a paragraph.  It starts with the start tag for
   the 'p' element, and it will end with the end tag for the 'p'
   element.</p>

 <p>This is another paragraph.  But this one is much shorter.</p>

   Some elements have no content. For example, in XHTML you can
   indicate that you want a horizontal line to appear in the
   document.

   For such elements, that have no content at all, XML introduced a
   shorthand form, which is ccompletely equivalent to the above form:

 <hr/>

   Example 3-2. Using an Element (Without Content)

   XHTML has an element for indicating a horizontal rule, called
   <hr>. This element does not wrap content, so it looks like this.

 <p>One paragraph.</p>
 <hr></hr>

 <p>This is another paragraph.  A horizontal rule separates this
   from the previous paragraph.</p>

   For such elements, that have no content at all, XML introduced a
   shorthand form, which is ccompletely equivalent to the above form:

 <p>One paragraph.</p>
 <hr/>

 <p>This is another paragraph.  A horizontal rule separates this
   from the previous paragraph.</p>

   If it is not obvious by now, elements can contain other elements.
   In the book example earlier, the book element contained all the
   chapter elements, which in turn contained all the paragraph
   elements, and so on.

   Example 3-3. Elements within Elements; <em>

 <p>This is a simple <em>paragraph</em> where some
   of the <em>words</em> have been <em>emphasized</em>.</p>

   The grammar will specify the rules detailing which elements can
   contain other elements, and exactly what they can contain.

     Important: People often confuse the terms tags and elements, and
     use the terms as if they were interchangeable. They are not.

     An element is a conceptual part of your document. An element has
     a defined start and end. The tags mark where the element starts
     and end.

     When this document (or anyone else knowledgeable about XML)
     refers to "the <p> tag" they mean the literal text consisting of
     the three characters <, p, and >. But the phrase "the <p>
     element" refers to the whole element.

     This distinction is very subtle. But keep it in mind.

   Elements can have attributes. An attribute has a name and a value,
   and is used for adding extra information to the element. This
   might be information that indicates how the content should be
   rendered, or might be something that uniquely identifies that
   occurrence of the element, or it might be something else.

   An element's attributes are written inside the start tag for that
   element, and take the form attribute-name="attribute-value".

   In XHTML, the <p> element has an attribute called <align>, which
   suggests an alignment (justification) for the paragraph to the
   program displaying the XHTML.

   The align attribute can take one of four defined values, left,
   center, right and justify. If the attribute is not specified then
   the default is left.

   Example 3-4. Using An Element with An Attribute

 <p align="left">The inclusion of the align attribute
   on this paragraph was superfluous, since the default is left.</p>

 <p align="center">This may appear in the center.</p>

   Some attributes will only take specific values, such as left or
   justify. Others will allow you to enter anything you want.

   Example 3-5. Single Quotes Around Attributes

 <p align='right'>I am on the right!</p>

   XML requires you to quote each attribute value with either single
   or double quotes. It is more habitual to use double quotes but you
   may use single quotes, as well. Using single quotes is practical
   if you want to include double quotes in the attribute value.

   The information on attributes, elements, and tags is stored in XML
   catalogs. The various Documentation Project tools use these
   catalog files to validate your work. The tools in textproc/docproj
   include a variety of XML catalog files. The FreeBSD Documentation
   Project includes its own set of catalog files. Your tools need to
   know about both sorts of catalog files.

     --------------------------------------------------------------

  3.2.1 For You to Do...

   In order to run the examples in this document you will need to
   install some software on your system and ensure that an
   environment variable is set correctly.

    1. Download and install textproc/docproj from the FreeBSD ports
       system. This is a meta-port that should download and install
       all of the programs and supporting files that are used by the
       Documentation Project.

    2. Add lines to your shell startup files to set
       SGML_CATALOG_FILES. (If you are not working on the English
       version of the documentation, you will want to substitute the
       correct directory for your language.)

       Example 3-6. .profile, for sh(1) and bash(1) Users

 SGML_ROOT=/usr/local/share/xml
 SGML_CATALOG_FILES=${SGML_ROOT}/jade/catalog
 SGML_CATALOG_FILES=${SGML_ROOT}/docbook/4.1/catalog:$SGML_CATALOG_FILES
 SGML_CATALOG_FILES=${SGML_ROOT}/html/catalog:$SGML_CATALOG_FILES
 SGML_CATALOG_FILES=${SGML_ROOT}/iso8879/catalog:$SGML_CATALOG_FILES
 SGML_CATALOG_FILES=/usr/doc/share/xml/catalog:$SGML_CATALOG_FILES
 SGML_CATALOG_FILES=/usr/doc/en_US.ISO8859-1/share/xml/catalog:$SGML_CATALOG_FILES
 export SGML_CATALOG_FILES

       Example 3-7. .cshrc, for csh(1) and tcsh(1) Users

 setenv SGML_ROOT /usr/local/share/xml
 setenv SGML_CATALOG_FILES ${SGML_ROOT}/jade/catalog
 setenv SGML_CATALOG_FILES ${SGML_ROOT}/docbook/4.1/catalog:$SGML_CATALOG_FILES
 setenv SGML_CATALOG_FILES ${SGML_ROOT}/html/catalog:$SGML_CATALOG_FILES
 setenv SGML_CATALOG_FILES ${SGML_ROOT}/iso8879/catalog:$SGML_CATALOG_FILES
 setenv SGML_CATALOG_FILES /usr/doc/share/xml/catalog:$SGML_CATALOG_FILES
 setenv SGML_CATALOG_FILES /usr/doc/en_US.ISO8859-1/share/xml/catalog:$SGML_CATALOG_FILES

       Then either log out, and log back in again, or run those
       commands from the command line to set the variable values.

    1. Create example.xml, and enter the following text:

 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

 <html xmlns="http://www.w3.org/1999/xhtml">
   <head>
     <title>An Example XHTML File</title>
   </head>

   <body>
     <p>This is a paragraph containing some text.</p>

     <p>This paragraph contains some more text.</p>

     <p align="right">This paragraph might be right-justified.</p>
   </body>
 </html>

    2. Try to validate this file using an XML parser.

       Part of textproc/docproj is the xmllint validating parser.

       Use xmllint in the following way to check that your document
       is valid:

 % xmllint --valid --noout example.xml

       As you will see, xmllint returns without displaying any
       output. This means that your document validated successfully.

    3. See what happens when required elements are omitted. Try
       removing the <title> and </title> tags, and re-run the
       validation.

 % xmllint --valid --noout example.xml
 example.xml:5: element head: validity error : Element head content does not follow the DTD, expecting ((script | style | meta | link | object | isindex)* , ((title , (script | style | meta | link | object | isindex)* , (base , (script | style | meta | link | object | isindex)*)?) | (base , (script | style | meta | link | object | isindex)* , title , (script | style | meta | link | object | isindex)*))), got ()

       This line tells you that the validation error comes from the
       fifth line of the example.xml file and that the content of the
       <head> is the part, which does not follow the rules described
       by the XHTML grammar.

       Below this line xmllint will show you the line where the error
       has been found and will also mark the exact character position
       with a ^ sign.

    4. Put the <title> element back in.

     --------------------------------------------------------------

3.3 The DOCTYPE Declaration

   The beginning of each document that you write may specify the name
   of the DTD that the document conforms to in case you use the DTD
   specification language. Other specification languages, like XML
   Schema and RELAX NG are not referred in the source document. This
   DOCTYPE declaration serves the XML parsers so that they can
   determine the DTD and ensure that the document does conform to it.

   A typical declaration for a document written to conform with
   version 1.0 of the XHTML DTD looks like this:

 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

   That line contains a number of different components.

   <!

           Is the indicator that indicates that this is an XML
           declaration. This line is declaring the document type.

   DOCTYPE

           Shows that this is an XML declaration for the document
           type.

   html

           Names the first element that will appear in the document.

   PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
   "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"

           Lists the Formal Public Identifier (FPI) for the DTD that
           this document conforms to. Your XML parser will use this
           to find the correct DTD when processing this document.

           PUBLIC is not a part of the FPI, but indicates to the XML
           processor how to find the DTD referenced in the FPI. Other
           ways of telling the XML parser how to find the DTD are
           shown later.

   "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"

           A local filename or an URL to find the DTD.

   >

           Returns to the document.

     --------------------------------------------------------------

  3.3.1 Formal Public Identifiers (FPIs)

     Note: You do not need to know this, but it is useful background,
     and might help you debug problems when your XML processor can
     not locate the DTD you are using.

   FPIs must follow a specific syntax. This syntax is as follows:

 "Owner//Keyword Description//Language"

   Owner

           This indicates the owner of the FPI.

           If this string starts with "ISO" then this is an ISO owned
           FPI. For example, the FPI "ISO 8879:1986//ENTITIES Greek
           Symbols//EN" lists ISO 8879:1986 as being the owner for
           the set of entities for Greek symbols. ISO 8879:1986 is
           the ISO number for the SGML standard, the predecessor (and
           a superset) of XML.

           Otherwise, this string will either look like -//Owner or
           +//Owner (notice the only difference is the leading + or
           -).

           If the string starts with - then the owner information is
           unregistered, with a + it identifies it as being
           registered.

           ISO 9070:1991 defines how registered names are generated;
           it might be derived from the number of an ISO publication,
           an ISBN code, or an organization code assigned according
           to ISO 6523. In addition, a registration authority could
           be created in order to assign registered names. The ISO
           council delegated this to the American National Standards
           Institute (ANSI).

           Because the FreeBSD Project has not been registered the
           owner string is -//FreeBSD. And as you can see, the W3C
           are not a registered owner either.

   Keyword

           There are several keywords that indicate the type of
           information in the file. Some of the most common keywords
           are DTD, ELEMENT, ENTITIES, and TEXT. DTD is used only for
           DTD files, ELEMENT is usually used for DTD fragments that
           contain only entity or element declarations. TEXT is used
           for XML content (text and tags).

   Description

           Any description you want to supply for the contents of
           this file. This may include version numbers or any short
           text that is meaningful to you and unique for the XML
           system.

   Language

           This is an ISO two-character code that identifies the
           native language for the file. EN is used for English.

     --------------------------------------------------------------

    3.3.1.1 catalog Files

   If you use the syntax above and process this document using an XML
   processor, the processor will need to have some way of turning the
   FPI into the name of the file on your computer that contains the
   DTD.

   In order to do this it can use a catalog file. A catalog file
   (typically called catalog) contains lines that map FPIs to
   filenames. For example, if the catalog file contained the line:

 PUBLIC  "-//W3C//DTD XHTML 1.0 Transitional//EN"             "1.0/transitional.dtd"

   The XML processor would know to look up the DTD from
   transitional.dtd in the 1.0 subdirectory of whichever directory
   held the catalog file that contained that line.

   Look at the contents of
   /usr/local/share/xml/dtd/xhtml/catalog.xml. This is the catalog
   file for the XHTML DTDs that will have been installed as part of
   the textproc/docproj port.

     --------------------------------------------------------------

    3.3.1.2 SGML_CATALOG_FILES

   In order to locate a catalog file, your XML processor will need to
   know where to look. Many of them feature command line parameters
   for specifying the path to one or more catalogs.

   In addition, you can set SGML_CATALOG_FILES to point to the files.
   This environment variable should consist of a colon-separated list
   of catalog files (including their full path).

   Typically, you will want to include the following files:

     * /usr/local/share/xml/docbook/4.1/catalog

     * /usr/local/share/xml/html/catalog

     * /usr/local/share/xml/iso8879/catalog

     * /usr/local/share/xml/jade/catalog

   You should already have done this.

     --------------------------------------------------------------

  3.3.2 Alternatives to FPIs

   Instead of using an FPI to indicate the DTD that the document
   conforms to (and therefore, which file on the system contains the
   DTD) you can explicitly specify the name of the file.

   The syntax for this is slightly different:

 <!DOCTYPE html SYSTEM "/path/to/file.dtd">

   The SYSTEM keyword indicates that the XML processor should locate
   the DTD in a system specific fashion. This typically (but not
   always) means the DTD will be provided as a filename.

   Using FPIs is preferred for reasons of portability. You do not
   want to have to ship a copy of the DTD around with your document,
   and if you used the SYSTEM identifier then everyone would need to
   keep their DTDs in the same place.

     --------------------------------------------------------------

3.4 Escaping Back to SGML

   As mentioned earlier, XML is only used when writing a DTD. This is
   not strictly true. There is certain XML syntax that you will want
   to be able to use within your documents. For example, comments can
   be included in your document, and will be ignored by the parser.
   Comments are entered using XML syntax. Other uses for XML syntax
   in your document will be shown later too.

   Obviously, you need some way of indicating to the XML processor
   that the following content is not elements within the document,
   but is XML that the parser should act upon.

   These sections are marked by <! ... > in your document. Everything
   between these delimiters is XML syntax as you might find within a
   DTD.

   As you may just have realized, the DOCTYPE declaration is an
   example of XML syntax that you need to include in your document...

     --------------------------------------------------------------

3.5 Comments

   Comments are an XML construction, and are normally only valid
   inside a DTD. However, as Section 3.4 shows, it is possible to use
   XML syntax within your document.

   The delimiter for XML comments is the string "--". The first
   occurrence of this string opens a comment, and the second closes
   it.

   Example 3-8. XML Generic Comment

 <!-- test comment -->

 <!-- This is inside the comment -->

 <!-- This is another comment    -->

 <!-- This is one way
      of doing multiline comments -->

 <!-- This is another way of   --
   -- doing multiline comments -->

   If you have used XHTML before you may have been shown different
   rules for comments. In particular, you may think that the string
   <!-- opens a comment, and it is only closed by -->.

   This is not the case. A lot of web browsers have broken XHTML
   parsers, and will accept that as valid. However, the XML parsers
   used by the Documentation Project are much stricter, and will
   reject documents that make that error.

   Example 3-9. Erroneous XML Comments

 <!-- This is in the comment --

      THIS IS OUTSIDE THE COMMENT!

   -- back inside the comment -->

   The XML parser will treat this as though it were actually:

 <!THIS IS OUTSIDE THE COMMENT>

   This is not valid XML, and may give confusing error messages.

 <!--------------- This is a very bad idea --------------->

   As the example suggests, do not write comments like that.

 <!--===================================================-->

   That is a (slightly) better approach, but it still potentially
   confusing to people new to XML.

     --------------------------------------------------------------

  3.5.1 For You to Do...

    1. Add some comments to example.xml, and check that the file
       still validates using xmllint.

    2. Add some invalid comments to example.xml, and see the error
       messages that xmllint gives when it encounters an invalid
       comment.

     --------------------------------------------------------------

3.6 Entities

   Entities are a mechanism for assigning names to chunks of content.
   As an XML parser processes your document, any entities it finds
   are replaced by the content of the entity.

   This is a good way to have re-usable, easily changeable chunks of
   content in your XML documents. It is also the only way to include
   one marked up file inside another using XML.

   There are two types of entities which can be used in two different
   situations; general entities and parameter entities.

     --------------------------------------------------------------

  3.6.1 General Entities

   You cannot use general entities in an XML context (although you
   define them in one). They can only be used in your document.
   Contrast this with parameter entities.

   Each general entity has a name. When you want to reference a
   general entity (and therefore include whatever text it represents
   in your document), you write &entity-name;. For example, suppose
   you had an entity called current.version which expanded to the
   current version number of your product. You could write:

 <para>The current version of our product is
   &current.version;.</para>

   When the version number changes you can simply change the
   definition of the value of the general entity and reprocess your
   document.

   You can also use general entities to enter characters that you
   could not otherwise include in an XML document. For example, < and
   & cannot normally appear in an XML document. When the XML parser
   sees the < symbol it assumes that a tag (either a start tag or an
   end tag) is about to appear, and when it sees the & symbol it
   assumes the next text will be the name of an entity.

   Fortunately, you can use the two general entities &lt; and &amp;
   whenever you need to include one or other of these.

   A general entity can only be defined within an XML context.
   Typically, this is done immediately after the DOCTYPE declaration.

   Example 3-10. Defining General Entities

 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
 "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd" [
 <!ENTITY current.version    "3.0-RELEASE">
 <!ENTITY last.version       "2.2.7-RELEASE">
 ]>

   Notice how the DOCTYPE declaration has been extended by adding a
   square bracket at the end of the first line. The two entities are
   then defined over the next two lines, before the square bracket is
   closed, and then the DOCTYPE declaration is closed.

   The square brackets are necessary to indicate that we are
   extending the DTD indicated by the DOCTYPE declaration.

     --------------------------------------------------------------

  3.6.2 Parameter Entities

   Like general entities, parameter entities are used to assign names
   to reusable chunks of text. However, whereas general entities can
   only be used within your document, parameter entities can only be
   used within an XML context.

   Parameter entities are defined in a similar way to general
   entities. However, instead of using &entity-name; to refer to
   them, use %entity-name; [1]. The definition also includes the %
   between the ENTITY keyword and the name of the entity.

   Example 3-11. Defining Parameter Entities

 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
 "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd" [
 <!ENTITY % param.some "some">
 <!ENTITY % param.text "text">
 <!ENTITY % param.new  "%param.some more %param.text">

 <!-- %param.new now contains "some more text" -->
 ]>

   This may not seem particularly useful. It will be.

     --------------------------------------------------------------

  3.6.3 For You to Do...

    1. Add a general entity to example.xml.

 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
 "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd" [
 <!ENTITY version "1.1">
 ]>

 <html xmlns="http://www.w3.org/1999/xhtml">
   <head>
     <title>An Example XHTML File</title>
   </head>

   <!-- You might well have some comments in here as well -->

   <body>
     <p>This is a paragraph containing some text.</p>

     <p>This paragraph contains some more text.</p>

     <p align="right">This paragraph might be right-justified.</p>

     <p>The current version of this document is: &version;</p>
   </body>
 </html>

    2. Validate the document using xmllint.

    3. Load example.xml into your web browser (you may need to copy
       it to example.html before your browser recognizes it as an
       XHTML document).

       Unless your browser is very advanced, you will not see the
       entity reference &version; replaced with the version number.
       Most web browsers have very simplistic parsers which do not
       handle XML DTD constructs. Furthermore, the closing ]< of the
       XML context are not recognized properly by browser and will
       probably be rendered.

    4. The solution is to normalize your document using an XML
       normalizer. The normalizer reads in valid XML and outputs
       equally valid XML which has been transformed in some way. One
       of the ways in which the normalizer transforms the XML is to
       expand all the entity references in the document, replacing
       the entities with the text that they represent.

       You can use xmllint to do this. It also has an option to drop
       the initial DTD section so that the closing ]< does not
       confuse browsers:

 % xmllint --noent --dropdtd example.xml > example.html

       You should find a normalized (i.e., entity references
       expanded) copy of your document in example.html, ready to load
       into your web browser.

     --------------------------------------------------------------

3.7 Using Entities to Include Files

   Entities (both general and parameter) are particularly useful when
   used to include one file inside another.

     --------------------------------------------------------------

  3.7.1 Using General Entities to Include Files

   Suppose you have some content for an XML book organized into
   files, one file per chapter, called chapter1.xml, chapter2.xml,
   and so forth, with a book.xml file that will contain these
   chapters.

   In order to use the contents of these files as the values for your
   entities, you declare them with the SYSTEM keyword. This directs
   the XML parser to use the contents of the named file as the value
   of the entity.

   Example 3-12. Using General Entities to Include Files

 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
 "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd" [
 <!ENTITY chapter.1 SYSTEM "chapter1.xml">
 <!ENTITY chapter.2 SYSTEM "chapter2.xml">
 <!ENTITY chapter.3 SYSTEM "chapter3.xml">
 <!-- And so forth -->
 ]>

 <html xmlns="http://www.w3.org/1999/xhtml">
   <!-- Use the entities to load in the chapters -->

   &chapter.1;
   &chapter.2;
   &chapter.3;
 </html>

     Warning: When using general entities to include other files
     within a document, the files being included (chapter1.xml,
     chapter2.xml, and so on) must not start with a DOCTYPE
     declaration. This is a syntax error because entities are
     low-level constructs and they are resolved before any parsing
     happens.

     --------------------------------------------------------------

  3.7.2 Using Parameter Entities to Include Files

   Recall that parameter entities can only be used inside an XML
   context. Why then would you want to include a file within an XML
   context?

   You can use this to ensure that you can reuse your general
   entities.

   Suppose that you had many chapters in your document, and you
   reused these chapters in two different books, each book organizing
   the chapters in a different fashion.

   You could list the entities at the top of each book, but this
   quickly becomes cumbersome to manage.

   Instead, place the general entity definitions inside one file, and
   use a parameter entity to include that file within your document.

   Example 3-13. Using Parameter Entities to Include Files

   First, place your entity definitions in a separate file, called
   chapters.ent. This file contains the following:

 <!ENTITY chapter.1 SYSTEM "chapter1.xml">
 <!ENTITY chapter.2 SYSTEM "chapter2.xml">
 <!ENTITY chapter.3 SYSTEM "chapter3.xml">

   Now create a parameter entity to refer to the contents of the
   file. Then use the parameter entity to load the file into the
   document, which will then make all the general entities available
   for use. Then use the general entities as before:

 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
 "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd" [
 <!-- Define a parameter entity to load in the chapter general entities -->
 <!ENTITY % chapters SYSTEM "chapters.ent">

 <!-- Now use the parameter entity to load in this file -->
 %chapters;
 ]>

 <html xmlns="http://www.w3.org/1999/xhtml">
   &chapter.1;
   &chapter.2;
   &chapter.3;
 </html>

     --------------------------------------------------------------

  3.7.3 For You to Do...

    3.7.3.1 Use General Entities to Include Files

    1. Create three files, para1.xml, para2.xml, and para3.xml.

       Put content similar to the following in each file:

 <p>This is the first paragraph.</p>

    2. Edit example.xml so that it looks like this:

 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
 "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd" [
 <!ENTITY version "1.1">
 <!ENTITY para1 SYSTEM "para1.xml">
 <!ENTITY para2 SYSTEM "para2.xml">
 <!ENTITY para3 SYSTEM "para3.xml">
 ]>

 <html xmlns="http://www.w3.org/1999/xhtml">
   <head>
     <title>An Example XHTML File</title>
   </head>

   <body>
     <p>The current version of this document is: &version;</p>

     &para1;
     &para2;
     &para3;
   </body>
 </html>

    3. Produce example.html by normalizing example.xml.

 % xmllint --dropdtd --noent example.xml > example.html

    4. Load example.html into your web browser, and confirm that the
       paran.xml files have been included in example.html.

     --------------------------------------------------------------

    3.7.3.2 Use Parameter Entities to Include Files

     Note: You must have taken the previous steps first.

    1. Edit example.xml so that it looks like this:

 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
 "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd" [
 <!ENTITY % entities SYSTEM "entities.ent"> %entities;
 ]>

 <html xmlns="http://www.w3.org/1999/xhtml">
   <head>
     <title>An Example XHTML File</title>
   </head>

   <body>
     <p>The current version of this document is: &version;</p>

     &para1;
     &para2;
     &para3;
   </body>
 </html>

    2. Create a new file, entities.ent, with this content:

 <!ENTITY version "1.1">
 <!ENTITY para1 SYSTEM "para1.xml">
 <!ENTITY para2 SYSTEM "para2.xml">
 <!ENTITY para3 SYSTEM "para3.xml">

    3. Produce example.html by normalizing example.xml.

 % xmllint --dropdtd --noent example.xml > example.html

    4. Load example.html into your web browser, and confirm that the
       paran.xml files have been included in example.html.

     --------------------------------------------------------------

3.8 Marked Sections

   XML provides a mechanism to indicate that particular pieces of the
   document should be processed in a special way. These are termed
   "marked sections".

   Example 3-14. Structure of A Marked Section

 <![KEYWORD[
   Contents of marked section
 ]]>

   As you would expect, being an XML construct, a marked section
   starts with <!.

   The first square bracket begins to delimit the marked section.

   KEYWORD describes how this marked section should be processed by
   the parser.

   The second square bracket indicates that the content of the marked
   section starts here.

   The marked section is finished by closing the two square brackets,
   and then returning to the document context from the XGML context
   with >.

     --------------------------------------------------------------

  3.8.1 Marked Section Keywords

    3.8.1.1 CDATA

   These keywords denote the marked sections content model, and allow
   you to change it from the default.

   When an XML parser is processing a document it keeps track of what
   is called the "content model".

   Briefly, the content model describes what sort of content the
   parser is expecting to see, and what it will do with it when it
   finds it.

   The content model you will probably find most useful is CDATA.

   CDATA is for "Character Data". If the parser is in this content
   model then it is expecting to see characters, and characters only.
   In this model the < and & symbols lose their special status, and
   will be treated as ordinary characters.

     Note: When you use CDATA in examples of text marked up in XML,
     keep in mind that the content of CDATA is not validated. You
     have to check the included XML text using other means. You
     could, for example, write the example in another document,
     validate the example code, and then paste it to your CDATA
     content.

   Example 3-15. Using a CDATA Marked Section

 <para>Here is an example of how you would include some text
   that contained many <literal>&lt;</literal>
   and <literal>&amp;</literal> symbols.  The sample
   text is a fragment of XHTML.  The surrounding text (<para> and
   <programlisting>) are from DocBook.</para>

 <programlisting>
   <![CDATA[
     <p>This is a sample that shows you some of the elements within
       XHTML.  Since the angle brackets are used so many times, it is
       simpler to say the whole example is a CDATA marked section
       than to use the entity names for the left and right angle
       brackets throughout.</p>

     <ul>
       <li>This is a listitem</li>
       <li>This is a second listitem</li>
       <li>This is a third listitem</li>
     </ul>

     <p>This is the end of the example.</p>
   ]]>
 </programlisting>

   If you look at the source for this document you will see this
   technique used throughout.

     --------------------------------------------------------------

    3.8.1.2 INCLUDE and IGNORE

   If the keyword is INCLUDE then the contents of the marked section
   will be processed. If the keyword is IGNORE then the marked
   section is ignored and will not be processed. It will not appear
   in the output.

   Example 3-16. Using INCLUDE and IGNORE in Marked Sections

 <![INCLUDE[
   This text will be processed and included.
 ]]>

 <![IGNORE[
   This text will not be processed or included.
 ]]>

   By itself, this is not too useful. If you wanted to remove text
   from your document you could cut it out, or wrap it in comments.

   It becomes more useful when you realize you can use parameter
   entities to control this, yet this usage is limited to entity
   files.

   For example, suppose that you produced a hard-copy version of some
   documentation and an electronic version. In the electronic version
   you wanted to include some extra content that was not to appear in
   the hard-copy.

   Create an entity file that defines general entities to include
   each chapter and guard these definitions with a parameter entity
   that can be set to either INCLUDE or IGNORE to control whether the
   entity is defined. After these conditional general entity
   definitions, place one more definition for each general entity to
   set them to an empty value. This technique makes use of the fact
   that entity definitions cannot be overridden but always the first
   definition takes effect. So you can control the inclusion of your
   chapter with the corrsponding parameter entity; if you set it to
   INCLUDE, the first general entity definition will be read and the
   second one will be ignored but if you set it to IGNORE, the first
   definition will be ignored and the second one will take effect.

   Example 3-17. Using A Parameter Entity to Control a Marked Section

 <!ENTITY % electronic.copy "INCLUDE">

 <![%electronic.copy;[
 <!ENTITY chap.preface   SYSTEM "preface.xml">
 ]]>

 <!ENTITY chap.preface "">

   When producing the hard-copy version, change the parameter
   entity's definition to:

 <!ENTITY % electronic.copy "IGNORE">

     --------------------------------------------------------------

  3.8.2 For You to Do...

    1. Modify the entities.ent file to contain the following:

 <!ENTITY version "1.1">
 <!ENTITY % conditional.text "IGNORE">

 <![%conditional.text;[
 <!ENTITY para1 SYSTEM "para1.xml">
 ]]>

 <!ENTITY para1 "">

 <!ENTITY para2 SYSTEM "para2.xml">
 <!ENTITY para3 SYSTEM "para3.xml">

    2. Normalize the example.xml file and notice that the conditional
       text is not present on the output document. Now if you set the
       parameter entity guard to INCLUDE and regenerate the
       normalized document, it will appear there again. Of course,
       this method makes more sense if you have more conditional
       chunks that depend on the same condition, for example, whether
       you are generating printed or online text.

     --------------------------------------------------------------

3.9 Conclusion

   That is the conclusion of this XML primer. For reasons of space
   and complexity several things have not been covered in depth (or
   at all). However, the previous sections cover enough XML for you
   to be able to follow the organization of the FDP documentation.

     --------------------------------------------------------------

                          Chapter 4 XML Markup

   This chapter describes the two markup languages you will encounter
   when you contribute to the FreeBSD documentation project. Each
   section describes the markup language, and details the markup that
   you are likely to want to use, or that is already in use.

   These markup languages contain a large number of elements, and it
   can be confusing sometimes to know which element to use for a
   particular situation. This section goes through the elements you
   are most likely to need, and gives examples of how you would use
   them.

   This is not an exhaustive list of elements, since that would just
   reiterate the documentation for each language. The aim of this
   section is to list those elements more likely to be useful to you.
   If you have a question about how best to markup a particular piece
   of content, please post it to the FreeBSD documentation project
   mailing list.

     Inline Versus Block: In the remainder of this document, when
     describing elements, inline means that the element can occur
     within a block element, and does not cause a line break. A block
     element, by comparison, will cause a line break (and other
     processing) when it is encountered.

     --------------------------------------------------------------

4.1 XHTML

   XHTML is the XML version of the HyperText Markup Language, which
   is the markup language of choice on the World Wide Web. More
   information can be found at http://www.w3.org/.

   XHTML is used to markup pages on the FreeBSD web site. It should
   not (generally) be used to mark up other documentation, since
   DocBook offers a far richer set of elements to choose from.
   Consequently, you will normally only encounter XHTML pages if you
   are writing for the web site.

   HTML has gone through a number of versions, 1, 2, 3.0, 3.2, 4.0
   and then an XML-compliant version has also been created, which is
   called XHTML and the latest widespread version of it is XHTML
   1.0(available in both strict and transitional variants).

   The XHTML DTDs are available from the Ports Collection in the
   textproc/xhtml port. They are automatically installed as part of
   the textproc/docproj port.

     --------------------------------------------------------------

  4.1.1 Formal Public Identifier (FPI)

   There are a number of XHTML FPIs, depending upon the version (also
   known as the level) of XHTML that you want to declare your
   document to be compliant with.

   The majority of XHTML documents on the FreeBSD web site comply
   with the transitional version of XHTML 1.0.

 PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"

     --------------------------------------------------------------

  4.1.2 Sectional Elements

   An XHTML document is normally split into two sections. The first
   section, called the head, contains meta-information about the
   document, such as its title, the name of the author, the parent
   document, and so on. The second section, the body, contains the
   content that will be displayed to the user.

   These sections are indicated with <head> and <body> elements
   respectively. These elements are contained within the top-level
   <html> element.

   Example 4-1. Normal XHTML Document Structure

 <html xmlns="http://www.w3.org/1999/xhtml">
   <head>
           <title>The Document's Title</title>
   </head>

   <body>

     ...

   </body>
 </html>

     --------------------------------------------------------------

  4.1.3 Block Elements

    4.1.3.1 Headings

   XHTML allows you to denote headings in your document, at up to six
   different levels.

   The largest and most prominent heading is <h1>, then <h2>,
   continuing down to <h6>.

   The element's content is the text of the heading.

   Example 4-2. <h1>, <h2>, and Other Header Tags

   Use:

 <h1>First section</h1>

 <!-- Document introduction goes here -->

 <h2>This is the heading for the first section</h2>

 <!-- Content for the first section goes here -->

 <h3>This is the heading for the first sub-section</h3>

 <!-- Content for the first sub-section goes here -->

 <h2>This is the heading for the second section</h2>

 <!-- Content for the second section goes here -->

   Generally, an XHTML page should have one first level heading
   (<h1>). This can contain many second level headings (<h2>), which
   can in turn contain many third level headings. Each <hn> element
   should have the same element, but one further up the hierarchy,
   preceding it. Leaving gaps in the numbering is to be avoided.

   Example 4-3. Bad Ordering of <hn> Elements

   Use:

 <h1>First section</h1>

 <!-- Document introduction -->

 <h3>Sub-section</h3>

 <!-- This is bad, <h2> has been left out -->

     --------------------------------------------------------------

    4.1.3.2 Paragraphs

   XHTML supports a single paragraph element, <p>.

   Example 4-4. <p>

   Use:

 <p>This is a paragraph.  It can contain just about any
   other element.</p>

     --------------------------------------------------------------

    4.1.3.3 Block Quotations

   A block quotation is an extended quotation from another document
   that should not appear within the current paragraph.

   Example 4-5. <blockquote>

   Use:

 <p>A small excerpt from the US Constitution:</p>

 <blockquote>We the People of the United States, in Order to form
   a more perfect Union, establish Justice, insure domestic
   Tranquility, provide for the common defence, promote the general
   Welfare, and secure the Blessings of Liberty to ourselves and our
   Posterity, do ordain and establish this Constitution for the
   United States of America.</blockquote>

     --------------------------------------------------------------

    4.1.3.4 Lists

   You can present the user with three types of lists, ordered,
   unordered, and definition.

   Typically, each entry in an ordered list will be numbered, while
   each entry in an unordered list will be preceded by a bullet
   point. Definition lists are composed of two sections for each
   entry. The first section is the term being defined, and the second
   section is the definition of the term.

   Ordered lists are indicated by the <ol> element, unordered lists
   by the <ul> element, and definition lists by the <dl> element.

   Ordered and unordered lists contain listitems, indicated by the
   <li> element. A listitem can contain textual content, or it may be
   further wrapped in one or more <p> elements.

   Definition lists contain definition terms (<dt>) and definition
   descriptions (<dd>). A definition term can only contain inline
   elements. A definition description can contain other block
   elements.

   Example 4-6. <ul> and <ol>

   Use:

 <p>An unordered list.  Listitems will probably be
   preceded by bullets.</p>

 <ul>
   <li>First item</li>

   <li>Second item</li>

   <li>Third item</li>
 </ul>

 <p>An ordered list, with list items consisting of multiple
   paragraphs.  Each item (note: not each paragraph) will be
   numbered.</p>

 <ol>
   <li><p>This is the first item.  It only has one paragraph.</p></li>

   <li><p>This is the first paragraph of the second item.</p>

     <p>This is the second paragraph of the second item.</p></li>

   <li><p>This is the first and only paragraph of the third
     item.</p></li>
 </ol>

   Example 4-7. Definition Lists with <dl>

   Use:

 <dl>
   <dt>Term 1</dt>

   <dd><p>Paragraph 1 of definition 1.</p>

     <p>Paragraph 2 of definition 1.</p></dd>

   <dt>Term 2</dt>

   <dd><p>Paragraph 1 of definition 2.</p></dd>

   <dt>Term 3</dt>

   <dd><p>Paragraph 1 of definition 3.</p></dd>
 </dl>

     --------------------------------------------------------------

    4.1.3.5 Pre-formatted Text

   You can indicate that text should be shown to the user exactly as
   it is in the file. Typically, this means that the text is shown in
   a fixed font, multiple spaces are not merged into one, and line
   breaks in the text are significant.

   In order to do this, wrap the content in the <pre> element.

   Example 4-8. <pre>

   You could use <pre> to mark up an email message:

 <pre>  From: nik@FreeBSD.org
   To: freebsd-doc@FreeBSD.org
   Subject: New documentation available

   There is a new copy of my primer for contributors to the FreeBSD
   Documentation Project available at

     &lt;URL:http://people.FreeBSD.org/~nik/primer/index.html&gt;

   Comments appreciated.

   N</pre>

   Keep in mind that < and & still are recognized as special
   characters in pre-formatted text. This is why the example shown
   had to use &lt; instead of <. For consistency, &gt; was used in
   place of >, too. Watch out for the special characters that may
   appear in text copied from a plain-text source, e.g., an email
   message or program code.

     --------------------------------------------------------------

    4.1.3.6 Tables

     Note: Most text-mode browsers (such as Lynx) do not render
     tables particularly effectively. If you are relying on the
     tabular display of your content, you should consider using
     alternative markup to prevent confusion.

   Mark up tabular information using the <table> element. A table
   consists of one or more table rows (<tr>), each containing one or
   more cells of table data (<td>). Each cell can contain other block
   elements, such as paragraphs or lists. It can also contain another
   table (this nesting can repeat indefinitely). If the cell only
   contains one paragraph then you do not need to include the <p>
   element.

   Example 4-9. Simple Use of <table>

   Use:

 <p>This is a simple 2x2 table.</p>

 <table>
   <tr>
     <td>Top left cell</td>

     <td>Top right cell</td>
   </tr>

   <tr>
     <td>Bottom left cell</td>

     <td>Bottom right cell</td>
   </tr>
 </table>

   A cell can span multiple rows and columns. To indicate this, add
   the rowspan and/or colspan attributes, with values indicating the
   number of rows or columns that should be spanned.

   Example 4-10. Using rowspan

   Use:

 <p>One tall thin cell on the left, two short cells next to
   it on the right.</p>

 <table>
   <tr>
     <td rowspan="2">Long and thin</td>
   </tr>

   <tr>
     <td>Top cell</td>

     <td>Bottom cell</td>
   </tr>
 </table>

   Example 4-11. Using colspan

   Use:

 <p>One long cell on top, two short cells below it.</p>

 <table>
   <tr>
     <td colspan="2">Top cell</td>
   </tr>

   <tr>
     <td>Bottom left cell</td>

     <td>Bottom right cell</td>
   </tr>
 </table>

   Example 4-12. Using rowspan and colspan Together

   Use:

 <p>On a 3x3 grid, the top left block is a 2x2 set of
   cells merged into one.  The other cells are normal.</p>

 <table>
   <tr>
     <td colspan="2" rowspan="2">Top left large cell</td>

     <td>Top right cell</td>
   </tr>

   <tr>
     <!-- Because the large cell on the left merges into
          this row, the first <td> will occur on its
          right -->

     <td>Middle right cell</td>
   </tr>

   <tr>
     <td>Bottom left cell</td>

     <td>Bottom middle cell</td>

     <td>Bottom right cell</td>
   </tr>
 </table>

     --------------------------------------------------------------

  4.1.4 In-line Elements

    4.1.4.1 Emphasizing Information

   You have two levels of emphasis available in XHTML, <em> and
   <strong>. <em> is for a normal level of emphasis and <strong>
   indicates stronger emphasis.

   Typically, <em> is rendered in italic and <strong> is rendered in
   bold. This is not always the case, however, and you should not
   rely on it. According to best practices, webpages only hold
   structural and semantical information and stylesheets are later
   applied to use these two so you should think of semantics not
   formatting when using these tags.

   Example 4-13. <em> and <strong>

   Use:

 <p><em>This</em> has been emphasized, while
   <strong>this</strong> has been strongly emphasized.</p>

     --------------------------------------------------------------

    4.1.4.2 Indicating Fixed-Pitch Text

   If you have content that should be rendered in a fixed pitch
   (typewriter) typeface, use <tt> (for "teletype").

   Example 4-14. <tt>

   Use:

 <p>This document was originally written by
   Nik Clayton, who can be reached by email as
   <tt>nik@FreeBSD.org</tt>.</p>

     --------------------------------------------------------------

  4.1.5 Links

     Note: Links are also inline elements.

     --------------------------------------------------------------

    4.1.5.1 Linking to Other Documents on the WWW

   In order to include a link to another document on the WWW you must
   know the URL of the document you want to link to.

   The link is indicated with <a>, and the href attribute contains
   the URL of the target document. The content of the element becomes
   the link, and is normally indicated to the user in some way
   (underlining, change of color, different mouse cursor when over
   the link, and so on).

   Example 4-15. Using <a href="...">

   Use:

 <p>More information is available at the
   <a href="http://www.FreeBSD.org/">FreeBSD web site</a>.</p>

   These links will take the user to the top of the chosen document.

     --------------------------------------------------------------

    4.1.5.2 Linking to Other Parts of Documents

   Linking to a point within another document (or within the same
   document) requires that the document author include anchors that
   you can link to.

   Anchors are indicated with <a> and the id attribute instead of
   href.

   Example 4-16. Using <a id="...">

   Use:

 <p><a id="para1">This</a> paragraph can be referenced
   in other links with the name <tt>para1</tt>.</p>

   To link to a named part of a document, write a normal link to that
   document, but include the id of the anchor after a # symbol.

   Example 4-17. Linking to a Named Part of Another Document

   Assume that the para1 example resides in a document called
   foo.html.

 <p>More information can be found in the
   <a href="foo.html#para1">first paragraph</a> of
   <tt>foo.html</tt>.</p>

   If you are linking to a named anchor within the same document then
   you can omit the document's URL, and just include the name of the
   anchor (with the preceding #).

   Example 4-18. Linking to a Named Part of the Same Document

   Assume that the para1 example resides in this document:

 <p>More information can be found in the
   <a href="#para1">first paragraph</a> of this
   document.</p>

     --------------------------------------------------------------

4.2 DocBook

   DocBook was originally developed by HaL Computer Systems and
   O'Reilly & Associates to be a DTD for writing technical
   documentation [2]. Since 1998 it is maintained by the   DocBook
   Technical Committee. As such, and unlike LinuxDoc and XHTML,
   DocBook is very heavily oriented towards markup that describes
   what something is, rather than describing how it should be
   presented.

     Formal Versus Informal: Some elements may exist in two forms,
     formal and informal. Typically, the formal version of the
     element will consist of a title followed by the informal version
     of the element. The informal version will not have a title.

   The DocBook DTD is available from the Ports Collection in the
   textproc/docbook port. It is automatically installed as part of
   the textproc/docproj port.

     --------------------------------------------------------------

  4.2.1 FreeBSD Extensions

   The FreeBSD Documentation Project has extended the DocBook DTD by
   adding some new elements. These elements serve to make some of the
   markup more precise.

   Where a FreeBSD specific element is listed below it is clearly
   marked.

   Throughout the rest of this document, the term "DocBook" is used
   to mean the FreeBSD extended DocBook DTD.

     Note: There is nothing about these extensions that is FreeBSD
     specific, it was just felt that they were useful enhancements
     for this particular project. Should anyone from any of the other
     *nix camps (NetBSD, OpenBSD, Linux, ...) be interested in
     collaborating on a standard DocBook extension set, please get in
     touch with Documentation Engineering Team <doceng@FreeBSD.org>.

   The FreeBSD extensions are not (currently) in the
   Ports Collection. They are stored in the FreeBSD Subversion tree,
   as head/share/xml/freebsd.dtd.

     --------------------------------------------------------------

  4.2.2 Formal Public Identifier (FPI)

   In compliance with the DocBook guidelines for writing FPIs for
   DocBook customizations, the FPI for the FreeBSD extended DocBook
   DTD is:

 PUBLIC "-//FreeBSD//DTD DocBook V4.2-Based Extension//EN"

     --------------------------------------------------------------

  4.2.3 Document Structure

   DocBook allows you to structure your documentation in several
   ways. In the FreeBSD Documentation Project we are using two
   primary types of DocBook document: the book and the article.

   A book is organized into <chapter>s. This is a mandatory
   requirement. There may be <part>s between the book and the chapter
   to provide another layer of organization. For example, the
   Handbook is arranged in this way.

   A chapter may (or may not) contain one or more sections. These are
   indicated with the <sect1> element. If a section contains another
   section then use the <sect2> element, and so on, up to <sect5>.

   Chapters and sections contain the remainder of the content.

   An article is simpler than a book, and does not use chapters.
   Instead, the content of an article is organized into one or more
   sections, using the same <sect1> (and <sect2> and so on) elements
   that are used in books.

   Obviously, you should consider the nature of the documentation you
   are writing in order to decide whether it is best marked up as a
   book or an article. Articles are well suited to information that
   does not need to be broken down into several chapters, and that
   is, relatively speaking, quite short, at up to 20-25 pages of
   content. Books are best suited to information that can be broken
   up into several chapters, possibly with appendices and similar
   content as well.

   The FreeBSD tutorials are all marked up as articles, while this
   document, the FreeBSD FAQ, and the FreeBSD Handbook are all marked
   up as books, for example.

     --------------------------------------------------------------

    4.2.3.1 Starting a Book

   The content of the book is contained within the <book> element. As
   well as containing structural markup, this element can contain
   elements that include additional information about the book. This
   is either meta-information, used for reference purposes, or
   additional content used to produce a title page.

   This additional information should be contained within <bookinfo>.

   Example 4-19. Boilerplate <book> with <bookinfo>

 <book>
   <bookinfo>
     <title>Your Title Here</title>

     <author>
       <firstname>Your first name</firstname>
       <surname>Your surname</surname>
       <affiliation>
         <address><email>Your email address</email></address>
       </affiliation>
     </author>

     <copyright>
       <year>1998</year>
       <holder role="mailto:your email address">Your name</holder>
     </copyright>

     <releaseinfo>$FreeBSD$</releaseinfo>

     <abstract>
       <para>Include an abstract of the book's contents here.</para>
     </abstract>
   </bookinfo>

   ...

 </book>

     --------------------------------------------------------------

    4.2.3.2 Starting an Article

   The content of the article is contained within the <article>
   element. As well as containing structural markup, this element can
   contain elements that include additional information about the
   article. This is either meta-information, used for reference
   purposes, or additional content used to produce a title page.

   This additional information should be contained within
   <articleinfo>.

   Example 4-20. Boilerplate <article> with <articleinfo>

 <article>
   <articleinfo>
     <title>Your title here</title>

     <author>
       <firstname>Your first name</firstname>
       <surname>Your surname</surname>
       <affiliation>
         <address><email>Your email address</email></address>
       </affiliation>
     </author>

     <copyright>
       <year>1998</year>
       <holder role="mailto:your email address">Your name</holder>
     </copyright>

     <releaseinfo>$FreeBSD$</releaseinfo>

     <abstract>
       <para>Include an abstract of the article's contents here.</para>
     </abstract>
   </articleinfo>

   ...

 </article>

     --------------------------------------------------------------

    4.2.3.3 Indicating Chapters

   Use <chapter> to mark up your chapters. Each chapter has a
   mandatory <title>. Articles do not contain chapters, they are
   reserved for books.

   Example 4-21. A Simple Chapter

 <chapter>
   <title>The Chapter's Title</title>

   ...
 </chapter>

   A chapter cannot be empty; it must contain elements in addition to
   <title>. If you need to include an empty chapter then just use an
   empty paragraph.

   Example 4-22. Empty Chapters

 <chapter>
   <title>This is An Empty Chapter</title>

   <para></para>
 </chapter>

     --------------------------------------------------------------

    4.2.3.4 Sections Below Chapters

   In books, chapters may (but do not need to) be broken up into
   sections, subsections, and so on. In articles, sections are the
   main structural element, and each article must contain at least
   one section. Use the <sectn> element. The n indicates the section
   number, which identifies the section level.

   The first <sectn> is <sect1>. You can have one or more of these in
   a chapter. They can contain one or more <sect2> elements, and so
   on, down to <sect5>.

   Example 4-23. Sections in Chapters

 <chapter>
   <title>A Sample Chapter</title>

   <para>Some text in the chapter.</para>

   <sect1>
     <title>First Section (1.1)</title>

     &hellip;
   </sect1>

   <sect1>
     <title>Second Section (1.2)</title>

     <sect2>
       <title>First Sub-Section (1.2.1)</title>

       <sect3>
         <title>First Sub-Sub-Section (1.2.1.1)</title>

         &hellip;
       </sect3>
     </sect2>

     <sect2>
       <title>Second Sub-Section (1.2.2)</title>

       &hellip;
     </sect2>
   </sect1>
 </chapter>

     Note: This example includes section numbers in the section
     titles. You should not do this in your documents. Adding the
     section numbers is carried out by the stylesheets (of which more
     later), and you do not need to manage them yourself.

     --------------------------------------------------------------

    4.2.3.5 Subdividing Using <part> Elements

   You can introduce another layer of organization between <book> and
   <chapter> with one or more <part>s. This cannot be done in an
   <article>.

 <part>
   <title>Introduction</title>

   <chapter>
     <title>Overview</title>

     ...
   </chapter>

   <chapter>
     <title>What is FreeBSD?</title>

     ...
   </chapter>

   <chapter>
     <title>History</title>

     ...
   </chapter>
 </part>

     --------------------------------------------------------------

  4.2.4 Block Elements

    4.2.4.1 Paragraphs

   DocBook supports three types of paragraphs: <formalpara>, <para>,
   and <simpara>.

   Most of the time you will only need to use <para>. <formalpara>
   includes a <title> element, and <simpara> disallows some elements
   from within <para>. Stick with <para>.

   Example 4-24. <para>

   Use:

 <para>This is a paragraph.  It can contain just about any
   other element.</para>

   Appearance:

   This is a paragraph. It can contain just about any other element.

     --------------------------------------------------------------

    4.2.4.2 Block Quotations

   A block quotation is an extended quotation from another document
   that should not appear within the current paragraph. You will
   probably only need it infrequently.

   Blockquotes can optionally contain a title and an attribution (or
   they can be left untitled and unattributed).

   Example 4-25. <blockquote>

   Use:

 <para>A small excerpt from the US Constitution:</para>

 <blockquote>
   <title>Preamble to the Constitution of the United States</title>

   <attribution>Copied from a web site somewhere</attribution>

   <para>We the People of the United States, in Order to form a more perfect
     Union, establish Justice, insure domestic Tranquility, provide for the
     common defence, promote the general Welfare, and secure the Blessings
     of Liberty to ourselves and our Posterity, do ordain and establish this
     Constitution for the United States of America.</para>
 </blockquote>

   Appearance:

   A small excerpt from the US Constitution:

     Preamble to the Constitution of the United States                
                                                                    
     We the People of the United States, in Order to form a more    
     perfect Union, establish Justice, insure domestic Tranquility, 
     provide for the common defence, promote the general Welfare,   
     and secure the Blessings of Liberty to ourselves and our       
     Posterity, do ordain and establish this Constitution for the   
     United States of America.                                      
                                 --Copied from a web site somewhere   

     --------------------------------------------------------------

    4.2.4.3 Tips, Notes, Warnings, Cautions, Important Information and
    Sidebars

   You may need to include extra information separate from the main
   body of the text. Typically this is "meta" information that the
   user should be aware of.

   Depending on the nature of the information, one of <tip>, <note>,
   <warning>, <caution>, and <important> should be used.
   Alternatively, if the information is related to the main text but
   is not one of the above, use <sidebar>.

   The circumstances in which to choose one of these elements over
   another is unclear. The DocBook documentation suggests:

     * A Note is for information that should be heeded by all
       readers.

     * An Important element is a variation on Note.

     * A Caution is for information regarding possible data loss or
       software damage.

     * A Warning is for information regarding possible hardware
       damage or injury to life or limb.

   Example 4-26. <warning>

   Use:

 <warning>
   <para>Installing FreeBSD may make you want to delete Windows from your
     hard disk.</para>
 </warning>

   Appearance:

     Warning: Installing FreeBSD may make you want to delete Windows
     from your hard disk.

     --------------------------------------------------------------

    4.2.4.4 Lists and Procedures

   You will often need to list pieces of information to the user, or
   present them with a number of steps that must be carried out in
   order to accomplish a particular goal.

   In order to do this, use <itemizedlist>, <orderedlist>, or
   <procedure>[3]

   <itemizedlist> and <orderedlist> are similar to their counterparts
   in HTML, <ul> and <ol>. Each one consists of one or more
   <listitem> elements, and each <listitem> contains one or more
   block elements. The <listitem> elements are analogous to HTML's
   <li> tags. However, unlike HTML, they are required.

   <procedure> is slightly different. It consists of <step>s, which
   may in turn consists of more <step>s or <substep>s. Each <step>
   contains block elements.

   Example 4-27. <itemizedlist>, <orderedlist>, and <procedure>

   Use:

 <itemizedlist>
   <listitem>
     <para>This is the first itemized item.</para>
   </listitem>

   <listitem>
     <para>This is the second itemized item.</para>
   </listitem>
 </itemizedlist>

 <orderedlist>
   <listitem>
     <para>This is the first ordered item.</para>
   </listitem>

   <listitem>
     <para>This is the second ordered item.</para>
   </listitem>
 </orderedlist>

 <procedure>
   <step>
     <para>Do this.</para>
   </step>

   <step>
     <para>Then do this.</para>
   </step>

   <step>
     <para>And now do this.</para>
   </step>
 </procedure>

   Appearance:

     * This is the first itemized item.

     * This is the second itemized item.

    1. This is the first ordered item.

    2. This is the second ordered item.

    1. Do this.

    2. Then do this.

    3. And now do this.

     --------------------------------------------------------------

    4.2.4.5 Showing File Samples

   If you want to show a fragment of a file (or perhaps a complete
   file) to the user, wrap it in the <programlisting> element.

   White space and line breaks within <programlisting> are
   significant. In particular, this means that the opening tag should
   appear on the same line as the first line of the output, and the
   closing tag should appear on the same line as the last line of the
   output, otherwise spurious blank lines may be included.

   Example 4-28. <programlisting>

   Use:

 <para>When you have finished, your program should look like
   this:</para>

 <programlisting>#include &lt;stdio.h&gt;

 int
 main(void)
 {
     printf("hello, world\n");
 }</programlisting>

   Notice how the angle brackets in the #include line need to be
   referenced by their entities instead of being included literally.

   Appearance:

   When you have finished, your program should look like this:

 #include <stdio.h>

 int
 main(void)
 {
     printf("hello, world\n");
 }

     --------------------------------------------------------------

    4.2.4.6 Callouts

   A callout is a mechanism for referring back to an earlier piece of
   text or specific position within an earlier example without
   linking to it within the text.

   To do this, mark areas of interest in your example
   (<programlisting>, <literallayout>, or whatever) with the <co>
   element. Each element must have a unique id assigned to it. After
   the example include a <calloutlist> that refers back to the
   example and provides additional commentary.

   Example 4-29. <co> and <calloutlist>

 <para>When you have finished, your program should look like
   this:</para>

 <programlisting>#include &lt;stdio.h&gt; <co id="co-ex-include"/>

 int <co id="co-ex-return"/>
 main(void)
 {
     printf("hello, world\n"); <co id="co-ex-printf"/>
 }</programlisting>

 <calloutlist>
   <callout arearefs="co-ex-include">
     <para>Includes the standard IO header file.</para>
   </callout>

   <callout arearefs="co-ex-return">
     <para>Specifies that <function>main()</function> returns an
       int.</para>
   </callout>

   <callout arearefs="co-ex-printf">
     <para>The <function>printf()</function> call that writes
       <literal>hello, world</literal> to standard output.</para>
   </callout>
 </calloutlist>

   Appearance:

   When you have finished, your program should look like this:

 #include <stdio.h> (1)

 int (2)
 main(void)
 {
     printf("hello, world\n"); (3)
 }

   (1)
           Includes the standard IO header file.
   (2)
           Specifies that main() returns an int.
   (3)
           The printf() call that writes hello, world to standard
           output.

     --------------------------------------------------------------

    4.2.4.7 Tables

   Unlike HTML, you do not need to use tables for layout purposes, as
   the stylesheet handles those issues for you. Instead, just use
   tables for marking up tabular data.

   In general terms (and see the DocBook documentation for more
   detail) a table (which can be either formal or informal) consists
   of a <table> element. This contains at least one <tgroup> element,
   which specifies (as an attribute) the number of columns in this
   table group. Within the tablegroup you can then have one <thead>
   element, which contains elements for the table headings (column
   headings), and one <tbody> which contains the body of the table.

   Both <tgroup> and <thead> contain <row> elements, which in turn
   contain <entry> elements. Each <entry> element specifies one cell
   in the table.

   Example 4-30. <informaltable>

   Use:

 <informaltable pgwide="1">
   <tgroup cols="2">
     <thead>
       <row>
         <entry>This is Column Head 1</entry>
         <entry>This is Column Head 2</entry>
       </row>
     </thead>

     <tbody>
       <row>
         <entry>Row 1, column 1</entry>
         <entry>Row 1, column 2</entry>
       </row>

       <row>
         <entry>Row 2, column 1</entry>
         <entry>Row 2, column 2</entry>
       </row>
     </tbody>
   </tgroup>
 </informaltable>

   Appearance:

   +----------------------------------------------------------------+
   |     This is Column Head 1      |     This is Column Head 2     |
   |--------------------------------+-------------------------------|
   | Row 1, column 1                | Row 1, column 2               |
   |--------------------------------+-------------------------------|
   | Row 2, column 1                | Row 2, column 2               |
   +----------------------------------------------------------------+

   Always use the pgwide attribute with a value of 1 with the
   <informaltable> element. A bug in Internet Explorer can cause the
   table to render incorrectly if this is omitted.

   If you do not want a border around the table the frame attribute
   can be added to the <informaltable> element with a value of none
   (i.e., <informaltable frame="none">).

   Example 4-31. Tables Where frame="none"

   Appearance:

         This is Column Head 1            This is Column Head 2       
   Row 1, column 1                   Row 1, column 2                  
   Row 2, column 1                   Row 2, column 2                  

     --------------------------------------------------------------

    4.2.4.8 Examples for the User to Follow

   A lot of the time you need to show examples for the user to
   follow. Typically, these will consist of dialogs with the
   computer; the user types in a command, the user gets a response
   back, they type in another command, and so on.

   A number of distinct elements and entities come into play here.

   <screen>

           Everything the user sees in this example will be on the
           computer screen, so the next element is <screen>.

           Within <screen>, white space is significant.

   <prompt>, &prompt.root; and &prompt.user;

           Some of the things the user will be seeing on the screen
           are prompts from the computer (either from the operating
           system, command shell, or application). These should be
           marked up using <prompt>.

           As a special case, the two shell prompts for the normal
           user and the root user have been provided as entities.
           Every time you want to indicate the user is at a shell
           prompt, use one of &prompt.root; and &prompt.user; as
           necessary. They do not need to be inside <prompt>.

             Note: &prompt.root; and &prompt.user; are FreeBSD
             extensions to DocBook, and are not part of the original
             DTD.

   <userinput>

           When displaying text that the user should type in, wrap it
           in <userinput> tags. It will probably be displayed
           differently to the user.

   Example 4-32. <screen>, <prompt>, and <userinput>

   Use:

 <screen>&prompt.user; <userinput>ls -1</userinput>
 foo1
 foo2
 foo3
 &prompt.user; <userinput>ls -1 | grep foo2</userinput>
 foo2
 &prompt.user; <userinput>su</userinput>
 <prompt>Password: </prompt>
 &prompt.root; <userinput>cat foo2</userinput>
 This is the file called 'foo2'</screen>

   Appearance:

 % ls -1
 foo1
 foo2
 foo3
 % ls -1 | grep foo2
 foo2
 % su
 Password:
 # cat foo2
 This is the file called 'foo2'

     Note: Even though we are displaying the contents of the file
     foo2, it is not marked up as <programlisting>. Reserve
     <programlisting> for showing fragments of files outside the
     context of user actions.

     --------------------------------------------------------------

  4.2.5 In-line Elements

    4.2.5.1 Emphasizing Information

   When you want to emphasize a particular word or phrase, use
   <emphasis>. This may be presented as italic, or bold, or might be
   spoken differently with a text-to-speech system.

   There is no way to change the presentation of the emphasis within
   your document, no equivalent of HTML's <b> and <i>. If the
   information you are presenting is important then consider
   presenting it in <important> rather than <emphasis>.

   Example 4-33. <emphasis>

   Use:

 <para>FreeBSD is without doubt <emphasis>the</emphasis>
   premiere Unix like operating system for the Intel architecture.</para>

   Appearance:

   FreeBSD is without doubt the premiere Unix like operating system
   for the Intel architecture.

     --------------------------------------------------------------

    4.2.5.2 Quotations

   To quote text from another document or source, or to denote a
   phrase that is used figuratively, use <quote>. Within a <quote>
   tag, you may use most of the markup tags available for normal
   text.

   Example 4-34. Quotations

   Use:

 <para>However, make sure that the search does not go beyond the
   <quote>boundary between local and public administration</quote>,
   as RFC 1535 calls it.</para>

   Appearance:

   However, make sure that the search does not go beyond the
   "boundary between local and public administration", as RFC 1535
   calls it.

     --------------------------------------------------------------

    4.2.5.3 Keys, Mouse Buttons, and Combinations

   To refer to a specific key on the keyboard, use <keycap>. To refer
   to a mouse button, use <mousebutton>. And to refer to combinations
   of key presses or mouse clicks, wrap them all in <keycombo>.

   <keycombo> has an attribute called action, which may be one of
   click, double-click, other, press, seq, or simul. The last two
   values denote whether the keys or buttons should be pressed in
   sequence, or simultaneously.

   The stylesheets automatically add any connecting symbols, such as
   +, between the key names, when wrapped in <keycombo>.

   Example 4-35. Keys, Mouse Buttons, and Combinations

   Use:

 <para>To switch to the second virtual terminal, press
   <keycombo action="simul"><keycap>Alt</keycap>
     <keycap>F1</keycap></keycombo>.</para>

 <para>To exit <command>vi</command> without saving your work, type
   <keycombo action="seq"><keycap>Esc</keycap><keycap>:</keycap>
     <keycap>q</keycap><keycap>!</keycap></keycombo>.</para>

 <para>My window manager is configured so that
   <keycombo action="simul"><keycap>Alt</keycap>
     <mousebutton>right</mousebutton>
   </keycombo> mouse button is used to move windows.</para>

   Appearance:

   To switch to the second virtual terminal, press Alt+F1.

   To exit vi without saving your work, type Esc : q !.

   My window manager is configured so that Alt+right mouse button is
   used to move windows.

     --------------------------------------------------------------

    4.2.5.4 Applications, Commands, Options, and Cites

   You will frequently want to refer to both applications and
   commands when writing documentation. The distinction between them
   is simple: an application is the name for a suite (or possibly
   just 1) of programs that fulfill a particular task. A command is
   the name of a program that the user can run.

   In addition, you will occasionally need to list one or more of the
   options that a command might take.

   Finally, you will often want to list a command with its manual
   section number, in the "command(number)" format so common in Unix
   manuals.

   Mark up application names with <application>.

   When you want to list a command with its manual section number
   (which should be most of the time) the DocBook element is
   <citerefentry>. This will contain a further two elements,
   <refentrytitle> and <manvolnum>. The content of <refentrytitle> is
   the name of the command, and the content of <manvolnum> is the
   manual page section.

   This can be cumbersome to write, and so a series of general
   entities have been created to make this easier. Each entity takes
   the form &man.manual-page.manual-section;.

   The file that contains these entities is in
   doc/share/xml/man-refs.ent, and can be referred to using this FPI:

 PUBLIC "-//FreeBSD//ENTITIES DocBook Manual Page Entities//EN"

   Therefore, the introduction to your documentation will probably
   look like this:

 <!DOCTYPE book PUBLIC "-//FreeBSD//DTD DocBook V4.1-Based Extension//EN" [

 <!ENTITY % man PUBLIC "-//FreeBSD//ENTITIES DocBook Manual Page Entities//EN">
 %man;

 ...

 ]>

   Use <command> when you want to include a command name "in-line"
   but present it as something the user should type in.

   Use <option> to mark up the options which will be passed to a
   command.

   When referring to the same command multiple times in close
   proximity it is preferred to use the &man.command.section;
   notation to markup the first reference and use <command> to markup
   subsequent references. This makes the generated output, especially
   HTML, appear visually better.

   This can be confusing, and sometimes the choice is not always
   clear. Hopefully this example makes it clearer.

   Example 4-36. Applications, Commands, and Options

   Use:

 <para><application>Sendmail</application> is the most
   widely used Unix mail application.</para>

 <para><application>Sendmail</application> includes the
   <citerefentry>
     <refentrytitle>sendmail</refentrytitle>
     <manvolnum>8</manvolnum>
   </citerefentry>, &man.mailq.1;, and &man.newaliases.1;
   programs.</para>

 <para>One of the command line parameters to <citerefentry>
     <refentrytitle>sendmail</refentrytitle>
     <manvolnum>8</manvolnum>
   </citerefentry>, <option>-bp</option>, will display the current
   status of messages in the mail queue.  Check this on the command
   line by running <command>sendmail -bp</command>.</para>

   Appearance:

   Sendmail is the most widely used Unix mail application.

   Sendmail includes the sendmail(8), mailq(1), and newaliases(1)
   programs.

   One of the command line parameters to sendmail(8), -bp, will
   display the current status of messages in the mail queue. Check
   this on the command line by running sendmail -bp.

     Note: Notice how the &man.command.section; notation is easier to
     follow.

     --------------------------------------------------------------

    4.2.5.5 Files, Directories, Extensions

   Whenever you wish to refer to the name of a file, a directory, or
   a file extension, use <filename>.

   Example 4-37. <filename>

   Use:

 <para>The SGML source for the Handbook in English can be
   found in <filename class="directory">/usr/doc/en_US.ISO8859-1/books/handbook/</filename>.  The first
   file is called <filename>book.xml</filename> in that
   directory.  You should also see a <filename>Makefile</filename>
   and a number of files with a <filename>.ent</filename>
   extension.</para>

   Appearance:

   The SGML source for the Handbook in English can be found in
   /usr/doc/en/handbook/. The first file is called handbook.xml in
   that directory. You should also see a Makefile and a number of
   files with a .ent extension.

     --------------------------------------------------------------

    4.2.5.6 The Name of Ports

     FreeBSD Extension: These elements are part of the FreeBSD
     extension to DocBook, and do not exist in the original DocBook
     DTD.

   You might need to include the name of a program from the FreeBSD
   Ports Collection in the documentation. Use the <filename> tag with
   the role attribute set to package to identify these. Since ports
   can be installed in any number of locations, only include the
   category and the port name; do not include /usr/ports.

   Example 4-38. <filename> Tag with package Role

   Use:

 <para>Install the <filename role="package">net/ethereal</filename> port to view network traffic.</para>

   Appearance:

   Install the net/ethereal port to view network traffic.

     --------------------------------------------------------------

    4.2.5.7 Devices

     FreeBSD Extension: These elements are part of the FreeBSD
     extension to DocBook, and do not exist in the original DocBook
     DTD.

   When referring to devices you have two choices. You can either
   refer to the device as it appears in /dev, or you can use the name
   of the device as it appears in the kernel. For this latter course,
   use <devicename>.

   Sometimes you will not have a choice. Some devices, such as
   networking cards, do not have entries in /dev, or the entries are
   markedly different from those entries.

   Example 4-39. <devicename>

   Use:

 <para><devicename>sio</devicename> is used for serial
   communication in FreeBSD.  <devicename>sio</devicename> manifests
   through a number of entries in <filename>/dev</filename>, including
   <filename>/dev/ttyd0</filename> and <filename>/dev/cuaa0</filename>.</para>

 <para>By contrast, the networking devices, such as
   <devicename>ed0</devicename> do not appear in <filename>/dev</filename>.</para>

 <para>In MS-DOS, the first floppy drive is referred to as
   <devicename>a:</devicename>.  In FreeBSD it is
   <filename>/dev/fd0</filename>.</para>

   Appearance:

   sio is used for serial communication in FreeBSD. sio manifests
   through a number of entries in /dev, including /dev/ttyd0 and
   /dev/cuaa0.

   By contrast, the networking devices, such as ed0 do not appear in
   /dev.

   In MS-DOS, the first floppy drive is referred to as a:. In FreeBSD
   it is /dev/fd0.

     --------------------------------------------------------------

    4.2.5.8 Hosts, Domains, IP Addresses, and So Forth

     FreeBSD Extension: These elements are part of the FreeBSD
     extension to DocBook, and do not exist in the original DocBook
     DTD.

   You can markup identification information for networked computers
   (hosts) in several ways, depending on the nature of the
   information. All of them use <hostid> as the element, with the
   role attribute selecting the type of the marked up information.

   No role attribute, or role="hostname"

           With no role attribute (i.e., <hostid>...</hostid>) the
           marked up information is the simple hostname, such as
           freefall or wcarchive. You can explicitly specify this
           with role="hostname".

   role="domainname"

           The text is a domain name, such as FreeBSD.org or
           ngo.org.uk. There is no hostname component.

   role="fqdn"

           The text is a Fully Qualified Domain Name, with both
           hostname and domain name parts.

   role="ipaddr"

           The text is an IP address, probably expressed as a dotted
           quad.

   role="ip6addr"

           The text is an IPv6 address.

   role="netmask"

           The text is a network mask, which might be expressed as a
           dotted quad, a hexadecimal string, or as a / followed by a
           number.

   role="mac"

           The text is an Ethernet MAC address, expressed as a series
           of 2 digit hexadecimal numbers separated by colons.

   Example 4-40. <hostid> and Roles

   Use:

 <para>The local machine can always be referred to by the
   name <hostid>localhost</hostid>, which will have the IP address
   <hostid role="ipaddr">127.0.0.1</hostid>.</para>

 <para>The <hostid role="domainname">FreeBSD.org</hostid> domain
   contains a number of different hosts, including
   <hostid role="fqdn">freefall.FreeBSD.org</hostid> and
   <hostid role="fqdn">pointyhat.FreeBSD.org</hostid>.</para>

 <para>When adding an IP alias to an interface (using
   <command>ifconfig</command>) <emphasis>always</emphasis> use a
   netmask of <hostid role="netmask">255.255.255.255</hostid>
   (which can also be expressed as <hostid
     role="netmask">0xffffffff</hostid>).</para>

 <para>The MAC address uniquely identifies every network card
   in existence.  A typical MAC address looks like <hostid
     role="mac">08:00:20:87:ef:d0</hostid>.</para>

   Appearance:

   The local machine can always be referred to by the name localhost,
   which will have the IP address 127.0.0.1.

   The FreeBSD.org domain contains a number of different hosts,
   including freefall.FreeBSD.org and bento.FreeBSD.org.

   When adding an IP alias to an interface (using ifconfig) always
   use a netmask of 255.255.255.255 (which can also be expressed as
   0xffffffff).

   The MAC address uniquely identifies every network card in
   existence. A typical MAC address looks like 08:00:20:87:ef:d0.

     --------------------------------------------------------------

    4.2.5.9 Usernames

     FreeBSD Extension: These elements are part of the FreeBSD
     extension to DocBook, and do not exist in the original DocBook
     DTD.

   When you need to refer to a specific username, such as root or
   bin, use <username>.

   Example 4-41. <username>

   Use:

 <para>To carry out most system administration functions you
   will need to be <username>root</username>.</para>

   Appearance:

   To carry out most system administration functions you will need to
   be root.

     --------------------------------------------------------------

    4.2.5.10 Describing Makefiles

     FreeBSD Extension: These elements are part of the FreeBSD
     extension to DocBook, and do not exist in the original DocBook
     DTD.

   Two elements exist to describe parts of Makefiles, <maketarget>
   and <makevar>.

   <maketarget> identifies a build target exported by a Makefile that
   can be given as a parameter to make. <makevar> identifies a
   variable that can be set (in the environment, on the make command
   line, or within the Makefile) to influence the process.

   Example 4-42. <maketarget> and <makevar>

   Use:

 <para>Two common targets in a <filename>Makefile</filename>
   are <maketarget>all</maketarget> and <maketarget>clean</maketarget>.</para>

 <para>Typically, invoking <maketarget>all</maketarget> will rebuild the
   application, and invoking <maketarget>clean</maketarget> will remove
   the temporary files (<filename>.o</filename> for example) created by
   the build process.</para>

 <para><maketarget>clean</maketarget> may be controlled by a number of
   variables, including <makevar>CLOBBER</makevar> and
   <makevar>RECURSE</makevar>.</para>

   Appearance:

   Two common targets in a Makefile are all and clean.

   Typically, invoking all will rebuild the application, and invoking
   clean will remove the temporary files (.o for example) created by
   the build process.

   clean may be controlled by a number of variables, including
   CLOBBER and RECURSE.

     --------------------------------------------------------------

    4.2.5.11 Literal Text

   You will often need to include "literal" text in the
   documentation. This is text that is excerpted from another file,
   or which should be copied from the documentation into another file
   verbatim.

   Some of the time, <programlisting> will be sufficient to denote
   this text. <programlisting> is not always appropriate,
   particularly when you want to include a portion of a file
   "in-line" with the rest of the paragraph.

   On these occasions, use <literal>.

   Example 4-43. <literal>

   Use:

 <para>The <literal>maxusers 10</literal> line in the kernel
   configuration file determines the size of many system tables, and is
   a rough guide to how many simultaneous logins the system will
   support.</para>

   Appearance:

   The maxusers 10 line in the kernel configuration file determines
   the size of many system tables, and is a rough guide to how many
   simultaneous logins the system will support.

     --------------------------------------------------------------

    4.2.5.12 Showing Items That the User Must Fill In

   There will often be times when you want to show the user what to
   do, or refer to a file, or command line, or similar, where the
   user cannot simply copy the examples that you provide, but must
   instead include some information themselves.

   <replaceable> is designed for this eventuality. Use it inside
   other elements to indicate parts of that element's content that
   the user must replace.

   Example 4-44. <replaceable>

   Use:

 <screen>&prompt.user; <userinput>man <replaceable>command</replaceable></userinput></screen>

   Appearance:

 % man command

   <replaceable> can be used in many different elements, including
   <literal>. This example also shows that <replaceable> should only
   be wrapped around the content that the user is meant to provide.
   The other content should be left alone.

   Use:

 <para>The <literal>maxusers <replaceable>n</replaceable></literal>
   line in the kernel configuration file determines the size of many system
   tables, and is a rough guide to how many simultaneous logins the system will
   support.</para>

 <para>For a desktop workstation, <literal>32</literal> is a good value
   for <replaceable>n</replaceable>.</para>

   Appearance:

   The maxusers n line in the kernel configuration file determines
   the size of many system tables, and is a rough guide to how many
   simultaneous logins the system will support.

   For a desktop workstation, 32 is a good value for n.

     --------------------------------------------------------------

    4.2.5.13 Quoting System Errors

   You might want to show errors generated by FreeBSD. Mark these
   with <errorname>. This indicates the exact error that appears.

   Example 4-45. <errorname>

   Use:

 <screen><errorname>Panic: cannot mount root</errorname></screen>

   Appearance:

 "Panic: cannot mount root"

     --------------------------------------------------------------

  4.2.6 Images

     Important: Image support in the documentation is currently
     extremely experimental. The mechanisms described here are
     unlikely to change, but that is not guaranteed.

     You will also need to install the graphics/ImageMagick port,
     which is used to convert between the different image formats.
     This is a big port, and most of it is not required. However,
     while we are working on the Makefiles and other infrastructure
     it makes things easier. This port is not in the textproc/docproj
     meta port, you must install it by hand.

     The best example of what follows in practice is the
     doc/en_US.ISO8859-1/articles/vm-design/ document. If you are
     unsure of the description that follows, take a look at the files
     in that directory to see how everything hangs together.
     Experiment with creating different formatted versions of the
     document to see how the image markup appears in the formatted
     output.

     --------------------------------------------------------------

    4.2.6.1 Image Formats

   We currently support two formats for images. The format you should
   use will depend on the nature of your image.

   For images that are primarily vector based, such as network
   diagrams, time lines, and similar, use Encapsulated Postscript,
   and make sure that your images have the .eps extension.

   For bitmaps, such as screen captures, use the Portable Network
   Graphic format, and make sure that your images have the .png
   extension.

   These are the only formats in which images should be committed to
   the Subversion repository.

   Use the right format for the right image. It is to be expected
   that your documentation will have a mix of EPS and PNG images. The
   Makefiles ensure that the correct format image is chosen depending
   on the output format that you use for your documentation. Do not
   commit the same image to the repository in two different formats.

     Important: It is anticipated that the Documentation Project will
     switch to using the Scalable Vector Graphic (SVG) format for
     vector images. However, the current state of SVG capable editing
     tools makes this impractical.

     --------------------------------------------------------------

    4.2.6.2 Markup

   The markup for an image is relatively simple. First, markup a
   <mediaobject>. The <mediaobject> can contain other, more specific
   objects. We are concerned with two, the <imageobject> and the
   <textobject>.

   You should include one <imageobject>, and two <textobject>
   elements. The <imageobject> will point to the name of the image
   file that will be used (without the extension). The <textobject>
   elements contain information that will be presented to the user as
   well as, or instead of, the image.

   There are two circumstances where this can happen.

     * When the reader is viewing the documentation in HTML. In this
       case, each image will need to have associated alternate text
       to show the user, typically whilst the image is loading, or if
       they hover the mouse pointer over the image.

     * When the reader is viewing the documentation in plain text. In
       this case, each image should have an ASCII art equivalent to
       show the user.

   An example will probably make things easier to understand. Suppose
   you have an image, called fig1, that you want to include in the
   document. This image is of a rectangle with an A inside it. The
   markup for this would be as follows.

 <mediaobject>
   <imageobject>
     <imagedata fileref="fig1"> (1)
   </imageobject>

   <textobject>
     <literallayout class="monospaced">+---------------+ (2)
 |       A       |
 +---------------+</literallayout>
   </textobject>

   <textobject>
     <phrase>A picture</phrase> (3)
   </textobject>
 </mediaobject>

   (1)
           Include an <imagedata> element inside the <imageobject>
           element. The fileref attribute should contain the filename
           of the image to include, without the extension. The
           stylesheets will work out which extension should be added
           to the filename automatically.
   (2)
           The first <textobject> should contain a <literallayout>
           element, where the class attribute is set to monospaced.
           This is your opportunity to demonstrate your ASCII art
           skills. This content will be used if the document is
           converted to plain text.

           Notice how the first and last lines of the content of the
           <literallayout> element butt up next to the element's
           tags. This ensures no extraneous white space is included.

   (3)
           The second <textobject> should contain a single <phrase>
           element. The contents of this will become the alt
           attribute for the image when this document is converted to
           HTML.

     --------------------------------------------------------------

    4.2.6.3 Makefile Entries

   Your images must be listed in the Makefile in the IMAGES variable.
   This variable should contain the name of all your source images.
   For example, if you have created three figures, fig1.eps,
   fig2.png, fig3.png, then your Makefile should have lines like this
   in it.

 ...
 IMAGES= fig1.eps fig2.png fig3.png
 ...

   or

 ...
 IMAGES=  fig1.eps
 IMAGES+= fig2.png
 IMAGES+= fig3.png
 ...

   Again, the Makefile will work out the complete list of images it
   needs to build your source document, you only need to list the
   image files you provided.

     --------------------------------------------------------------

    4.2.6.4 Images and Chapters in Subdirectories

   You must be careful when you separate your documentation into
   smaller files (see Section 3.7.1) in different directories.

   Suppose you have a book with three chapters, and the chapters are
   stored in their own directories, called chapter1/chapter.xml,
   chapter2/chapter.xml, and chapter3/chapter.xml. If each chapter
   has images associated with it, it is suggested to place those
   images in each chapter's subdirectory (chapter1/, chapter2/, and
   chapter3/).

   However, if you do this you must include the directory names in
   the IMAGES variable in the Makefile, and you must include the
   directory name in the <imagedata> element in your document.

   For example, if you have chapter1/fig1.png, then
   chapter1/chapter.xml should contain:

 <mediaobject>
   <imageobject>
     <imagedata fileref="chapter1/fig1"> (1)
   </imageobject>

   ...

 </mediaobject>

   (1)
           The directory name must be included in the fileref
           attribute.

   The Makefile must contain:

 ...
 IMAGES=  chapter1/fig1.png
 ...

   Then everything should just work.

     --------------------------------------------------------------

  4.2.7 Links

     Note: Links are also in-line elements.

     --------------------------------------------------------------

    4.2.7.1 Linking to Other Parts of the Same Document

   Linking within the same document requires you to specify where you
   are linking from (i.e., the text the user will click, or otherwise
   indicate, as the source of the link) and where you are linking to
   (the link's destination).

   Each element within DocBook has an attribute called id. You can
   place text in this attribute to uniquely name the element it is
   attached to.

   This value will be used when you specify the link source.

   Normally, you will only be linking to chapters or sections, so you
   would add the id attribute to these elements.

   Example 4-46. Attribute id on Chapters and Sections

 <chapter id="chapter1">
   <title>Introduction</title>

   <para>This is the introduction.  It contains a subsection,
     which is identified as well.</para>

   <sect1 id="chapter1-sect1">
     <title>Sub-sect 1</title>

     <para>This is the subsection.</para>
   </sect1>
 </chapter>

   Obviously, you should use more descriptive values. The values must
   be unique within the document (i.e., not just the file, but the
   document the file might be included in as well). Notice how the id
   for the subsection is constructed by appending text to the id of
   the chapter. This helps to ensure that they are unique.

   If you want to allow the user to jump into a specific portion of
   the document (possibly in the middle of a paragraph or an
   example), use <anchor>. This element has no content, but takes an
   id attribute.

   Example 4-47. <anchor>

 <para>This paragraph has an embedded
   <anchor id="para1">link target in it.  It will not show up in
   the document.</para>

   When you want to provide the user with a link they can activate
   (probably by clicking) to go to a section of the document that has
   an id attribute, you can use either <xref> or <link>.

   Both of these elements have a linkend attribute. The value of this
   attribute should be the value that you have used in a id attribute
   (it does not matter if that value has not yet occurred in your
   document; this will work for forward links as well as backward
   links).

   If you use <xref> then you have no control over the text of the
   link. It will be generated for you.

   Example 4-48. Using <xref>

   Assume that this fragment appears somewhere in a document that
   includes the id example:

 <para>More information can be found
   in <xref linkend="chapter1"/>.</para>

 <para>More specific information can be found
   in <xref linkend="chapter1-sect1"/>.</para>

   The text of the link will be generated automatically, and will
   look like (emphasized text indicates the text that will be the
   link):

     More information can be found in Chapter One.

     More specific information can be found in the section called
     Sub-Sect 1.

   Notice how the text from the link is derived from the section
   title or the chapter number.

     Note: This means that you cannot use <xref> to link to an id
     attribute on an <anchor> element. The <anchor> has no content,
     so the <xref> cannot generate the text for the link.

   If you want to control the text of the link then use <link>. This
   element wraps content, and the content will be used for the link.

   Example 4-49. Using <link>

   Assume that this fragment appears somewhere in a document that
   includes the id example.

 <para>More information can be found in
   <link linkend="chapter1">the first chapter</link>.</para>

 <para>More specific information can be found in
   <link linkend="chapter1-sect1">this</link> section.</para>

   This will generate the following (emphasized text indicates the
   text that will be the link):

     More information can be found in the first chapter.

     More specific information can be found in this section.

     Note: That last one is a bad example. Never use words like
     "this" or "here" as the source for the link. The reader will
     need to hunt around the surrounding context to see where the
     link is actually taking them.

     Note: You can use <link> to include a link to an id on an
     <anchor> element, since the <link> content defines the text that
     will be used for the link.

     --------------------------------------------------------------

    4.2.7.2 Linking to Documents on the WWW

   Linking to external documents is much simpler, as long as you know
   the URL of the document you want to link to. Use <ulink>. The url
   attribute is the URL of the page that the link points to, and the
   content of the element is the text that will be displayed for the
   user to activate.

   Example 4-50. <ulink>

   Use:

 <para>Of course, you could stop reading this document and
   go to the <ulink url="&url.base;/index.html">FreeBSD
   home page</ulink> instead.</para>

   Appearance:

   Of course, you could stop reading this document and go to the
   FreeBSD home page instead.

     --------------------------------------------------------------

                        Chapter 5 * Stylesheets

   SGML says nothing about how a document should be displayed to the
   user, or rendered on paper. To do that, various languages have
   been developed to describe stylesheets, including DynaText,
   Panorama, SPICE, JSSS, FOSI, CSS, and DSSSL.

   For DocBook, we are using stylesheets written in DSSSL. For XHTML
   we are using CSS.

     --------------------------------------------------------------

5.1 * DSSSL

   The Documentation Project uses a slightly customized version of
   Norm Walsh's modular DocBook stylesheets.

   These can be found in textproc/dsssl-docbook-modular.

   The modified stylesheets are not in the ports system. Instead they
   are part of the Documentation Project source repository, and can
   be found in doc/share/xml/freebsd.dsl. It is well commented, and
   pending completion of this section you are encouraged to examine
   that file to see how some of the available options in the standard
   stylesheets have been configured in order to customize the output
   for the FreeBSD Documentation Project. That file also contains
   examples showing how to extend the elements that the stylesheet
   understands, which is how the FreeBSD specific elements have been
   formatted.

     --------------------------------------------------------------

5.2 CSS

   Cascading Stylesheets (CSS) are a mechanism for attaching style
   information (font, weight, size, color, and so forth) to elements
   in an XHTML document without abusing XHTML to do so.

     --------------------------------------------------------------

  5.2.1 The DocBook Documents

   The FreeBSD DSSSL stylesheets include a reference to a stylesheet,
   docbook.css, which is expected to appear in the same directory as
   the XHTML files. The project-wide CSS file is copied from
   doc/share/misc/docbook.css when documents are converted to XHTML,
   and is installed automatically.

     --------------------------------------------------------------

               Chapter 6 Structuring Documents Under doc/

   The doc/ tree is organized in a particular fashion, and the
   documents that are part of the FDP are in turn organized in a
   particular fashion. The aim is to make it simple to add new
   documentation into the tree and:

    1. Make it easy to automate converting the document to other
       formats.

    2. Promote consistency between the different documentation
       organizations, to make it easier to switch between working on
       different documents.

    3. Make it easy to decide where in the tree new documentation
       should be placed.

   In addition, the documentation tree has to accommodate
   documentation that could be in many different languages and in
   many different encodings. It is important that the structure of
   the documentation tree does not enforce any particular defaults or
   cultural preferences.

     --------------------------------------------------------------

6.1 The Top Level, doc/

   There are two types of directory under doc/, each with very
   specific directory names and meanings.

   Directory: share/

   Meaning: Contains files that are not specific to the various
   translations and encodings of the documentation. Contains
   subdirectories to further categorize the information. For example,
   the files that comprise the make(1) infrastructure are in
   share/mk, while the additional XML support files (such as the
   FreeBSD extended DocBook DTD) are in share/xml.

   Directory: lang.encoding/

   Meaning: One directory exists for each available translation and
   encoding of the documentation, for example en_US.ISO8859-1/ and
   zh_TW.Big5/. The names are long, but by fully specifying the
   language and encoding we prevent any future headaches should a
   translation team want to provide the documentation in the same
   language but in more than one encoding. This also completely
   isolates us from any problems that might be caused by a switch to
   Unicode.

     --------------------------------------------------------------

6.2 The lang.encoding/ Directories

   These directories contain the documents themselves. The
   documentation is split into up to three more categories at this
   level, indicated by the different directory names.

   Directory: articles

   Contents: Documentation marked up as a DocBook <article> (or
   equivalent). Reasonably short, and broken up into sections.
   Normally only available as one XHTML file.

   Directory: books

   Contents: Documentation marked up as a DocBook <book> (or
   equivalent). Book length, and broken up into chapters. Normally
   available as both one large XHTML file (for people with fast
   connections, or who want to print it easily from a browser) and as
   a collection of linked, smaller files.

   Directory: man

   Contents: For translations of the system manual pages. This
   directory will contain one or more mann directories, corresponding
   to the sections that have been translated.

   Not every lang.encoding directory will contain all of these
   directories. It depends on how much translation has been
   accomplished by that translation team.

     --------------------------------------------------------------

6.3 Document Specific Information

   This section contains specific notes about particular documents
   managed by the FDP.

     --------------------------------------------------------------

  6.3.1 The Handbook

   books/handbook/

   The Handbook is written to comply with the FreeBSD DocBook
   extended DTD.

   The Handbook is organized as a DocBook <book>. It is then divided
   into <part>s, each of which may contain several <chapter>s.
   <chapter>s are further subdivided into sections (<sect1>) and
   subsections (<sect2>, <sect3>) and so on.

     --------------------------------------------------------------

    6.3.1.1 Physical Organization

   There are a number of files and directories within the handbook
   directory.

     Note: The Handbook's organization may change over time, and this
     document may lag in detailing the organizational changes. If you
     have any questions about how the Handbook is organized, please
     contact the FreeBSD documentation project mailing list.

     --------------------------------------------------------------

      6.3.1.1.1 Makefile

   The Makefile defines some variables that affect how the XML source
   is converted to other formats, and lists the various source files
   that make up the Handbook. It then includes the standard
   doc.project.mk file, to bring in the rest of the code that handles
   converting documents from one format to another.

     --------------------------------------------------------------

      6.3.1.1.2 book.xml

   This is the top level document in the Handbook. It contains the
   Handbook's DOCTYPE declaration, as well as the elements that
   describe the Handbook's structure.

   book.xml uses parameter entities to load in the files with the
   .ent extension. These files (described later) then define general
   entities that are used throughout the rest of the Handbook.

     --------------------------------------------------------------

      6.3.1.1.3 directory/chapter.xml

   Each chapter in the Handbook is stored in a file called
   chapter.xml in a separate directory from the other chapters. Each
   directory is named after the value of the id attribute on the
   <chapter> element.

   For example, if one of the chapter files contains:

 <chapter id="kernelconfig">
 ...
 </chapter>

   Then it will be called chapter.xml in the kernelconfig directory.
   In general, the entire contents of the chapter will be held in
   this file.

   When the XHTML version of the Handbook is produced, this will
   yield kernelconfig.html. This is because of the id value, and is
   not related to the name of the directory.

   In earlier versions of the Handbook the files were stored in the
   same directory as book.xml, and named after the value of the id
   attribute on the file's <chapter> element. Now, it is possible to
   include images in each chapter. Images for each Handbook chapter
   are stored within share/images/books/handbook. Note that localized
   version of these images should be placed in the same directory as
   the XML sources for each chapter. Namespace collisions would be
   inevitable, and it is easier to work with several directories with
   a few files in them than it is to work with one directory that has
   many files in it.

   A brief look will show that there are many directories with
   individual chapter.xml files, including basics/chapter.xml,
   introduction/chapter.xml, and printing/chapter.xml.

     Important: Chapters and/or directories should not be named in a
     fashion that reflects their ordering within the Handbook. This
     ordering might change as the content within the Handbook is
     reorganized; this sort of reorganization should not (generally)
     include the need to rename files (unless entire chapters are
     being promoted or demoted within the hierarchy).

   Each chapter.xml file will not be a complete XML document. In
   particular, they will not have their own DOCTYPE lines at the
   start of the files.

   This is unfortunate as it makes it impossible to treat these as
   generic XML files and simply convert them to HTML, RTF, PS, and
   other formats in the same way the main Handbook is generated. This
   would force you to rebuild the Handbook every time you want to see
   the effect a change has had on just one chapter.

     --------------------------------------------------------------

               Chapter 7 The Documentation Build Process

   This chapter's main purpose is to clearly explain how the
   documentation build process is organized, and how to affect
   modifications to this process.

   After you have finished reading this chapter you should:

     * Know what you need to build the FDP documentation, in addition
       to those mentioned in the XML tools chapter.

     * Be able to read and understand the make instructions that are
       present in each document's Makefiles, as well as an overview
       of the doc.project.mk includes.

     * Be able to customize the build process by using make variables
       and make targets.

     --------------------------------------------------------------

7.1 The FreeBSD Documentation Build Toolset

   Here are your tools. Use them every way you can.

     * The primary build tool you will need is make, but specifically
       Berkeley Make.

     * Package building is handled by FreeBSD's pkg_create. If you
       are not using FreeBSD, you will either have to live without
       packages, or compile the source yourself.

     * gzip is needed to create compressed versions of the document.
       bzip2 compression and zip archives are also supported. tar is
       supported, but package building demands it.

     * install is the default method to install the documentation.
       There are alternatives, however.

     Note: It is unlikely you will have any trouble finding these
     last two, they are mentioned for completeness only.

     --------------------------------------------------------------

7.2 Understanding Makefiles in the Documentation Tree

   There are three main types of Makefiles in the FreeBSD
   Documentation Project tree.

     * Subdirectory Makefiles simply pass commands to those
       directories below them.

     * Documentation Makefiles describe the document(s) that should
       be produced from this directory.

     * Make includes are the glue that perform the document
       production, and are usually of the form doc.xxx.mk.

     --------------------------------------------------------------

  7.2.1 Subdirectory Makefiles

   These Makefiles usually take the form of:

 SUBDIR =articles
 SUBDIR+=books

 COMPAT_SYMLINK = en

 DOC_PREFIX?= ${.CURDIR}/..
 .include "${DOC_PREFIX}/share/mk/doc.project.mk"

   In quick summary, the first four non-empty lines define the make
   variables, SUBDIR, COMPAT_SYMLINK, and DOC_PREFIX.

   The first SUBDIR statement, as well as the COMPAT_SYMLINK
   statement, shows how to assign a value to a variable, overriding
   any previous value.

   The second SUBDIR statement shows how a value is appended to the
   current value of a variable. The SUBDIR variable is now articles
   books.

   The DOC_PREFIX assignment shows how a value is assigned to the
   variable, but only if it is not already defined. This is useful if
   DOC_PREFIX is not where this Makefile thinks it is - the user can
   override this and provide the correct value.

   Now what does it all mean? SUBDIR mentions which subdirectories
   below this one the build process should pass any work on to.

   COMPAT_SYMLINK is specific to compatibility symlinks (amazingly
   enough) for languages to their official encoding (doc/en would
   point to en_US.ISO-8859-1).

   DOC_PREFIX is the path to the root of the FreeBSD Document Project
   tree. This is not always that easy to find, and is also easily
   overridden, to allow for flexibility. .CURDIR is a make builtin
   variable with the path to the current directory.

   The final line includes the FreeBSD Documentation Project's
   project-wide make system file doc.project.mk which is the glue
   which converts these variables into build instructions.

     --------------------------------------------------------------

  7.2.2 Documentation Makefiles

   These Makefiles set a bunch of make variables that describe how to
   build the documentation contained in that directory.

   Here is an example:

 MAINTAINER=nik@FreeBSD.org

 DOC?= book

 FORMATS?= html-split html

 INSTALL_COMPRESSED?= gz
 INSTALL_ONLY_COMPRESSED?=

 # SGML content
 SRCS=  book.xml

 DOC_PREFIX?= ${.CURDIR}/../../..

 .include "$(DOC_PREFIX)/share/mk/docproj.docbook.mk"

   The MAINTAINER variable is a very important one. This variable
   provides the ability to claim ownership over a document in the
   FreeBSD Documentation Project, whereby you gain the responsibility
   for maintaining it.

   DOC is the name (sans the .xml extension) of the main document
   created by this directory. SRCS lists all the individual files
   that make up the document. This should also include important
   files in which a change should result in a rebuild.

   FORMATS indicates the default formats that should be built for
   this document. INSTALL_COMPRESSED is the default list of
   compression techniques that should be used in the document build.
   INSTALL_ONLY_COMPRESS, empty by default, should be non-empty if
   only compressed documents are desired in the build.

     Note: We covered optional variable assignments in the previous
     section.

   The DOC_PREFIX and include statements should be familiar already.

     --------------------------------------------------------------

7.3 FreeBSD Documentation Project Make Includes

   This is best explained by inspection of the code. Here are the
   system include files:

     * doc.project.mk is the main project include file, which
       includes all the following include files, as necessary.

     * doc.subdir.mk handles traversing of the document tree during
       the build and install processes.

     * doc.install.mk provides variables that affect ownership and
       installation of documents.

     * doc.docbook.mk is included if DOCFORMAT is docbook and DOC is
       set.

     --------------------------------------------------------------

  7.3.1 doc.project.mk

   By inspection:

 DOCFORMAT?=     docbook
 MAINTAINER?=    doc@FreeBSD.org

 PREFIX?=        /usr/local
 PRI_LANG?=      en_US.ISO8859-1

 .if defined(DOC)
 .if ${DOCFORMAT} == "docbook"
 .include "doc.docbook.mk"
 .endif
 .endif

 .include "doc.subdir.mk"
 .include "doc.install.mk"

     --------------------------------------------------------------

    7.3.1.1 Variables

   DOCFORMAT and MAINTAINER are assigned default values, if these are
   not set by the document make file.

   PREFIX is the prefix under which the documentation building tools
   are installed. For normal package and port installation, this is
   /usr/local.

   PRI_LANG should be set to whatever language and encoding is
   natural amongst users these documents are being built for. US
   English is the default.

     Note: PRI_LANG in no way affects what documents can, or even
     will, be built. Its main use is creating links to commonly
     referenced documents into the FreeBSD documentation install
     root.

     --------------------------------------------------------------

    7.3.1.2 Conditionals

   The .if defined(DOC) line is an example of a make conditional
   which, like in other programs, defines behavior if some condition
   is true or if it is false. defined is a function which returns
   whether the variable given is defined or not.

   .if ${DOCFORMAT} == "docbook", next, tests whether the DOCFORMAT
   variable is "docbook", and in this case, includes doc.docbook.mk.

   The two .endifs close the two above conditionals, marking the end
   of their application.

     --------------------------------------------------------------

  7.3.2 doc.subdir.mk

   This is too long to explain by inspection, you should be able to
   work it out with the knowledge gained from the previous chapters,
   and a little help given here.

     --------------------------------------------------------------

    7.3.2.1 Variables

     * SUBDIR is a list of subdirectories that the build process
       should go further down into.

     * ROOT_SYMLINKS is the name of directories that should be linked
       to the document install root from their actual locations, if
       the current language is the primary language (specified by
       PRI_LANG).

     * COMPAT_SYMLINK is described in the Subdirectory Makefile
       section.

     --------------------------------------------------------------

    7.3.2.2 Targets and Macros

   Dependencies are described by target: dependency1 dependency2 ...
   tuples, where to build target, you need to build the given
   dependencies first.

   After that descriptive tuple, instructions on how to build the
   target may be given, if the conversion process between the target
   and its dependencies are not previously defined, or if this
   particular conversion is not the same as the default conversion
   method.

   A special dependency .USE defines the equivalent of a macro.

 _SUBDIRUSE: .USE
 .for entry in ${SUBDIR}
         @${ECHO} "===> ${DIRPRFX}${entry}"
         @(cd ${.CURDIR}/${entry} && \
         ${MAKE} ${.TARGET:S/realpackage/package/:S/realinstall/install/} DIRPRFX=${DIRPRFX}${entry}/ )
 .endfor

   In the above, _SUBDIRUSE is now a macro which will execute the
   given commands when it is listed as a dependency.

   What sets this macro apart from other targets? Basically, it is
   executed after the instructions given in the build procedure it is
   listed as a dependency to, and it does not adjust .TARGET, which
   is the variable which contains the name of the target currently
   being built.

 clean: _SUBDIRUSE
         rm -f ${CLEANFILES}

   In the above, clean will use the _SUBDIRUSE macro after it has
   executed the instruction rm -f ${CLEANFILES}. In effect, this
   causes clean to go further and further down the directory tree,
   deleting built files as it goes down, not on the way back up.

     --------------------------------------------------------------

      7.3.2.2.1 Provided Targets

     * install and package both go down the directory tree calling
       the real versions of themselves in the subdirectories
       (realinstall and realpackage respectively).

     * clean removes files created by the build process (and goes
       down the directory tree too). cleandir does the same, and also
       removes the object directory, if any.

     --------------------------------------------------------------

    7.3.2.3 More on Conditionals

     * exists is another condition function which returns true if the
       given file exists.

     * empty returns true if the given variable is empty.

     * target returns true if the given target does not already
       exist.

     --------------------------------------------------------------

    7.3.2.4 Looping Constructs in make (.for)

   .for provides a way to repeat a set of instructions for each
   space-separated element in a variable. It does this by assigning a
   variable to contain the current element in the list being
   examined.

 _SUBDIRUSE: .USE
 .for entry in ${SUBDIR}
         @${ECHO} "===> ${DIRPRFX}${entry}"
         @(cd ${.CURDIR}/${entry} && \
         ${MAKE} ${.TARGET:S/realpackage/package/:S/realinstall/install/} DIRPRFX=${DIRPRFX}${entry}/ )
 .endfor

   In the above, if SUBDIR is empty, no action is taken; if it has
   one or more elements, the instructions between .for and .endfor
   would repeat for every element, with entry being replaced with the
   value of the current element.

     --------------------------------------------------------------

                         Chapter 8 The Website

8.1 Preparation

   Use a disk with sufficient free space. You may need anything from
   200 MB to over 500 MB, depending on the method you choose. This
   space will hold the XML tools, a subset of the svn tree, temporary
   build space and the installed web pages.

     Note: Make sure your documentation ports are up to date! When in
     doubt, remove the old ports using pkg_delete(1) command before
     installing the port. For example, we currently depend on
     jade-1.2 and if you have installed jade-1.1, please do:

 # pkg_delete jade-1.1

     --------------------------------------------------------------

  8.1.1 Using svn

   svn is necessary to "check out" the necessary files from the doc/
   Subversion repository. svn can be installed with pkg_add(1) or
   from the FreeBSD Ports Collection by running:

 # cd /usr/ports/devel/subversion
 # make install clean

   To check out the full source files for the FreeBSD website, run:

 # svn checkout https://svn0.us-east.FreeBSD.org/doc/head/ /usr/build

   svn0.us-east.FreeBSD.org is a public SVN server. Select the
   closest mirror and verify the mirror server certificate from the
   list of Subversion mirror sites.

     Tip: If svn is not run as root, be sure /usr/build has the
     proper permissions for the current user. If changing the
     permissions is not possible, use a different target directory
     for the website files.

   When svn finishes, the current version of the FreeBSD website will
   exist within /usr/build. If a different target directory was used,
   replace /usr/build appropriately throughout the remainder of this
   document.

   That's it! You can now proceed with the website build.

     --------------------------------------------------------------

8.2 Build the Web Pages from Scratch

   Having completed the necessary steps to obtain the website source
   files, the website can be built. In our example, the build
   directory is /usr/build and all the required files are already in
   place.

    1. Change into the build directory:

 # cd /usr/build

    2. The website build starts from the en_US.ISO8859-1/htdocs
       directory by executing the make(1) all target, to create the
       web pages.

 # cd en_US.ISO8859-1/htdocs
 # make all

         Tip: The build requires a few files from the Ports
         Collection and may fail without a properly configured Ports
         CVS mirror. Set the NOPORTSCVS environment variable as
         described in Section 8.4 to use your local Ports Collection
         (typically /usr/ports) instead.

     --------------------------------------------------------------

8.3 Install the Web Pages into Your Web Server

    1. If you have moved out of the en_US.ISO8859-1/htdocs directory,
       change back to it.

 # cd /usr/build/en_US.ISO8859-1/htdocs

    2. Run the make(1) install target, setting the DESTDIR variable
       to the name of the directory you want to install the files to.
       The actual files are installed under $DESTDIR/data which
       should be configured as your web server's document root.

 # env DESTDIR=/usr/local/www make install

    3. If you have previously installed the web pages into the same
       directory the install process will not have deleted any old or
       outdated pages. For example, if you build and install a new
       copy of the site every day, this command will find and delete
       all files that have not been updated in three days.

 # find /usr/local/www -ctime 3 -print0 | xargs -0 rm

     --------------------------------------------------------------

8.4 Environment Variables

   ENGLISH_ONLY

           If set and not empty, the makefiles will build and install
           only the English documents. All translations will be
           ignored. E.g.:

 # make ENGLISH_ONLY=YES all install

           If you want to unset the variable ENGLISH_ONLY and build
           all pages, including translations, set the variable
           ENGLISH_ONLY to an empty value:

 # make ENGLISH_ONLY="" all install clean

   WEB_ONLY

           If set and not empty, the Makefiles will build and install
           only the HTML pages from the en_US.ISO8859-1/htdocs
           directory. All other directories within en_US.ISO8859-1
           (Handbook, FAQ, Tutorials) will be ignored. E.g.:

 # make WEB_ONLY=YES all install

   WEB_LANG

           If set, the Makefiles will build and install only for the
           languages specified by this variable inside the /usr/build
           directory. All other languages except English will be
           ignored. E.g.:

 # make WEB_LANG="el_GR.ISO8859-7 es_ES.ISO8859-1 hu_HU.ISO8859-2 nl_NL.ISO8859-1" all install

   NOPORTSCVS

           If set, the Makefiles will not checkout files from the
           ports CVS repository. Instead, it will copy the files from
           /usr/ports (or where the variable PORTSBASE points to).

   WEB_ONLY, WEB_LANG, ENGLISH_ONLY and NOPORTSCVS are make
   variables. You can set the variables in /etc/make.conf,
   Makefile.inc, as environment variables on the command line, or in
   your dot files.

     --------------------------------------------------------------

                         Chapter 9 Translations

   This is the FAQ for people translating the FreeBSD documentation
   (FAQ, Handbook, tutorials, manual pages, and others) to different
   languages.

   It is very heavily based on the translation FAQ from the FreeBSD
   German Documentation Project, originally written by Frank Gru:nder
   <elwood@mc5sys.in-berlin.de> and translated back to English by
   Bernd Warken <bwarken@mayn.de>.

   The FAQ is maintained by the Documentation Engineering Team
   <doceng@FreeBSD.org>.

   9.1. Why a FAQ?

   9.2. What do i18n and l10n mean?

   9.3. Is there a mailing list for translators?

   9.4. Are more translators needed?

   9.5. What languages do I need to know?

   9.6. What software do I need to know?

   9.7. How do I find out who else might be translating to the same
   language?

   9.8. No one else is translating to my language. What do I do?

   9.9. I have translated some documentation, where do I send it?

   9.10. I am the only person working on translating to this
   language, how do I submit my translation?

   9.11. Can I include language or country specific text in my
   translation?

   9.12. How should language specific characters be included?

   9.13. Addressing the reader

   9.14. Do I need to include any additional information in my
   translations?

   9.1. Why a FAQ?

   More and more people are approaching the freebsd-doc mailing list
   and volunteering to translate FreeBSD documentation to other
   languages. This FAQ aims to answer their questions so they can
   start translating documentation as quickly as possible.

   9.2. What do i18n and l10n mean?

   i18n means internationalization and l10n means localization. They
   are just a convenient shorthand.

   i18n can be read as "i" followed by 18 letters, followed by "n".
   Similarly, l10n is "l" followed by 10 letters, followed by "n".

   9.3. Is there a mailing list for translators?

   Yes. Different translation groups have their own mailing lists.
   The list of translation projects has more information about the
   mailing lists and web sites run by each translation project.

   9.4. Are more translators needed?

   Yes. The more people work on translation the faster it gets done,
   and the faster changes to the English documentation are mirrored
   in the translated documents.

   You do not have to be a professional translator to be able to
   help.

   9.5. What languages do I need to know?

   Ideally, you will have a good knowledge of written English, and
   obviously you will need to be fluent in the language you are
   translating to.

   English is not strictly necessary. For example, you could do a
   Hungarian translation of the FAQ from the Spanish translation.

   9.6. What software do I need to know?

   It is strongly recommended that you maintain a local copy of the
   FreeBSD Subversion repository (at least the documentation part).
   This can be done by running:

 % svn checkout https://svn0.us-east.FreeBSD.org/doc/head/ head

   svn0.us-east.FreeBSD.org is a public SVN server. Select the
   closest mirror and verify the mirror server certificate from the
   list of Subversion mirror sites.

     Note: This will require the devel/subversion package to be
     installed.

   You should be comfortable using svn. This will allow you to see
   what has changed between different versions of the files that make
   up the documentation.

   For example, to view the differences between revisions r33733 and
   r33734 of en_US.ISO8859-1/books/fdp-primer/book.xml, run:

 % svn diff -r33733:33734 en_US.ISO8859-1/books/fdp-primer/book.xml

   9.7. How do I find out who else might be translating to the same
   language?

   The Documentation Project translations page lists the translation
   efforts that are currently known about. If others are already
   working on translating documentation to your language, please do
   not duplicate their efforts. Instead, contact them to see how you
   can help.

   If no one is listed on that page as translating for your language,
   then send a message to the FreeBSD documentation project mailing
   list in case someone else is thinking of doing a translation, but
   has not announced it yet.

   9.8. No one else is translating to my language. What do I do?

   Congratulations, you have just started the "FreeBSD
   your-language-here Documentation Translation Project". Welcome
   aboard.

   First, decide whether or not you have got the time to spare. Since
   you are the only person working on your language at the moment it
   is going to be your responsibility to publicize your work and
   coordinate any volunteers that might want to help you.

   Write an email to the Documentation Project mailing list,
   announcing that you are going to translate the documentation, so
   the Documentation Project translations page can be maintained.

   If there is already someone in your country providing FreeBSD
   mirroring services you should contact them and ask if you can have
   some webspace for your project, and possibly an email address or
   mailing list services.

   Then pick a document and start translating. It is best to start
   with something fairly small-either the FAQ, or one of the
   tutorials.

   9.9. I have translated some documentation, where do I send it?

   That depends. If you are already working with a translation team
   (such as the Japanese team, or the German team) then they will
   have their own procedures for handling submitted documentation,
   and these will be outlined on their web pages.

   If you are the only person working on a particular language (or
   you are responsible for a translation project and want to submit
   your changes back to the FreeBSD project) then you should send
   your translation to the FreeBSD project (see the next question).

   9.10. I am the only person working on translating to this
   language, how do I submit my translation?

   or

   We are a translation team, and want to submit documentation that
   our members have translated for us.

   First, make sure your translation is organized properly. This
   means that it should drop into the existing documentation tree and
   build straight away.

   Currently, the FreeBSD documentation is stored in a top level
   directory called head/. Directories below this are named according
   to the language code they are written in, as defined in ISO639
   (/usr/share/misc/iso639 on a version of FreeBSD newer than 20th
   January 1999).

   If your language can be encoded in different ways (for example,
   Chinese) then there should be directories below this, one for each
   encoding format you have provided.

   Finally, you should have directories for each document.

   For example, a hypothetical Swedish translation might look like:

 head/
     sv_SE.ISO8859-1/
                      Makefile
                      htdocs/
                            docproj/
                      books/
                            faq/
                                Makefile
                                book.xml

   sv_SE.ISO8859-1 is the name of the translation, in lang.encoding
   form. Note the two Makefiles, which will be used to build the
   documentation.

   Use tar(1) and gzip(1) to compress up your documentation, and send
   it to the project.

 % cd doc
 % tar cf swedish-docs.tar sv_SE.ISO8859-1
 % gzip -9 swedish-docs.tar

   Put swedish-docs.tar.gz somewhere. If you do not have access to
   your own webspace (perhaps your ISP does not let you have any)
   then you can email Documentation Engineering Team
   <doceng@FreeBSD.org>, and arrange to email the files when it is
   convenient.

   Either way, you should use send-pr(1) to submit a report
   indicating that you have submitted the documentation. It would be
   very helpful if you could get other people to look over your
   translation and double check it first, since it is unlikely that
   the person committing it will be fluent in the language.

   Someone (probably the Documentation Project Manager, currently
   Documentation Engineering Team <doceng@FreeBSD.org>) will then
   take your translation and confirm that it builds. In particular,
   the following things will be looked at:

    1. Do all your files use RCS strings (such as "ID")?

    2. Does make all in the sv_SE.ISO8859-1 directory work correctly?

    3. Does make install work correctly?

   If there are any problems then whoever is looking at the
   submission will get back to you to work them out.

   If there are no problems your translation will be committed as
   soon as possible.

   9.11. Can I include language or country specific text in my
   translation?

   We would prefer that you did not.

   For example, suppose that you are translating the Handbook to
   Korean, and want to include a section about retailers in Korea in
   your Handbook.

   There is no real reason why that information should not be in the
   English (or German, or Spanish, or Japanese, or ...) versions as
   well. It is feasible that an English speaker in Korea might try to
   pick up a copy of FreeBSD whilst over there. It also helps
   increase FreeBSD's perceived presence around the globe, which is
   not a bad thing.

   If you have country specific information, please submit it as a
   change to the English Handbook (using send-pr(1)) and then
   translate the change back to your language in the translated
   Handbook.

   Thanks.

   9.12. How should language specific characters be included?

   Non-ASCII characters in the documentation should be included using
   SGML entities.

   Briefly, these look like an ampersand (&), the name of the entity,
   and a semi-colon (;).

   The entity names are defined in ISO8879, which is in the ports
   tree as textproc/iso8879.

   A few examples include:

   Entity: &eacute;

   Appearance: e

   Description: Small "e" with an acute accent

   Entity: &Eacute;

   Appearance: E

   Description: Large "E" with an acute accent

   Entity: &uuml;

   Appearance: u:

   Description: Small "u" with an umlaut

   After you have installed the iso8879 port, the files in
   /usr/local/share/xml/iso8879 contain the complete list.

   9.13. Addressing the reader

   In the English documents, the reader is addressed as "you", there
   is no formal/informal distinction as there is in some languages.

   If you are translating to a language which does distinguish, use
   whichever form is typically used in other technical documentation
   in your language. If in doubt, use a mildly polite form.

   9.14. Do I need to include any additional information in my
   translations?

   Yes.

   The header of the English version of each document will look
   something like this:

 <!--
      The FreeBSD Documentation Project

      $FreeBSD: head/en_US.ISO8859-1/books/faq/book.xml 38674 2012-04-14 13:52:52Z $
 -->

   The exact boilerplate may change, but it will always include a
   $FreeBSD$ line and the phrase The FreeBSD Documentation Project.
   Note that the $FreeBSD part is expanded automatically by
   Subversion, so it should be empty (just $FreeBSD$) for new files.

   Your translated documents should include their own $FreeBSD$ line,
   and change the FreeBSD Documentation Project line to The FreeBSD
   language Documentation Project.

   In addition, you should add a third line which indicates which
   revision of the English text this is based on.

   So, the Spanish version of this file might start:

 <!--
      The FreeBSD Spanish Documentation Project

      $FreeBSD: head/es_ES.ISO8859-1/books/faq/book.xml 38826 2012-05-17 19:12:14Z hrs $
      Original revision: r38674
 -->

     --------------------------------------------------------------

                        Chapter 10 Writing Style

   In order to promote consistency between the myriad authors of the
   FreeBSD documentation, some guidelines have been drawn up for
   authors to follow.

   Use American English Spelling

           There are several variants of English, with different
           spellings for the same word. Where spellings differ, use
           the American English variant. "color", not "colour",
           "rationalize", not "rationalise", and so on.

             Note: The use of British English may be accepted in the
             case of a contributed article, however the spelling must
             be consistent within the whole document. The other
             documents such as books, web site, manual pages, etc.
             will have to use American English.

   Do not use contractions

           Do not use contractions. Always spell the phrase out in
           full. "Don't use contractions" would be wrong.

           Avoiding contractions makes for a more formal tone, is
           more precise, and is slightly easier for translators.

   Use the serial comma

           In a list of items within a paragraph, separate each item
           from the others with a comma. Separate the last item from
           the others with a comma and the word "and".

           For example, look at the following:

             This is a list of one, two and three items.

           Is this a list of three items, "one", "two", and "three",
           or a list of two items, "one" and "two and three"?

           It is better to be explicit and include a serial comma:

             This is a list of one, two, and three items.

   Avoid redundant phrases

           Try not to use redundant phrases. In particular, "the
           command", "the file", and "man command" are probably
           redundant.

           These two examples show this for commands. The second
           example is preferred.

           Use the command svn to update your sources.

           Use svn to update your sources.

           These two examples show this for filenames. The second
           example is preferred.

           ... in the filename /etc/rc.local...

           ... in /etc/rc.local...

           These two examples show this for manual references. The
           second example is preferred (the second example uses
           <citerefentry>).

           See man csh for more information.

           See csh(1).

   Two spaces at the end of sentences

           Always use two spaces at the end of sentences, as this
           improves readability, and eases use of tools such as
           Emacs.

           While it may be argued that a capital letter following a
           period denotes a new sentence, this is not the case,
           especially in name usage. "Jordan K. Hubbard" is a good
           example; it has a capital H following a period and a
           space, and there certainly is not a new sentence there.

   For more information about writing style, see Elements of Style,
   by William Strunk.

     --------------------------------------------------------------

10.1 Style Guide

   To keep the source for the documentation consistent when many
   different people are editing it, please follow these style
   conventions.

     --------------------------------------------------------------

  10.1.1 Letter Case

   Tags are entered in lower case, <para>, not <PARA>.

   Text that appears in SGML contexts is generally written in upper
   case, <!ENTITY...>, and <!DOCTYPE...>, not <!entity...> and
   <!doctype...>.

     --------------------------------------------------------------

  10.1.2 Acronyms

   Acronyms should generally be spelled out the first time they
   appear in a document, as in: "Network Time Protocol (NTP)". After
   the acronym has been defined, you should generally use the acronym
   only (not the whole term, unless it makes more sense contextually
   to use the whole term). Usually, acronyms are defined only one per
   document. But if you prefer, you can also define them the first
   time they appear in each chapter.

   The first three uses of an acronym should be enclosed in <acronym>
   tags, with a role attribute with the full term defined. This
   allows a link to the glossary to be created, and for mouseovers to
   be rendered with the fully expanded term.

     --------------------------------------------------------------

  10.1.3 Indentation

   Each file starts with indentation set at column 0, regardless of
   the indentation level of the file which might contain this one.

   Opening tags increase the indentation level by 2 spaces. Closing
   tags decrease the indentation level by 2 spaces. Blocks of 8
   spaces at the start of a line should be replaced with a tab. Do
   not use spaces in front of tabs, and do not add extraneous
   whitespace at the end of a line. Content within elements should be
   indented by two spaces if the content runs over more than one
   line.

   For example, the source for this section looks something like:

 +--- This is column 0
 V
 <chapter>
   <title>...</title>

   <sect1>
     <title>...</title>

     <sect2>
       <title>Indentation</title>

       <para>Each file starts with indentation set at column 0,
         <emphasis>regardless</emphasis> of the indentation level of the file
         which might contain this one.</para>

       ...
     </sect2>
   </sect1>
 </chapter>

   If you use Emacs or XEmacs to edit the files then sgml-mode should
   be loaded automatically, and the Emacs local variables at the
   bottom of each file should enforce these styles.

   Vim users might want to configure their editor with:

 augroup sgmledit
   autocmd FileType sgml set formatoptions=cq2l " Special formatting options
   autocmd FileType sgml set textwidth=70       " Wrap lines at 70 columns
   autocmd FileType sgml set shiftwidth=2       " Automatically indent
   autocmd FileType sgml set softtabstop=2      " Tab key indents 2 spaces
   autocmd FileType sgml set tabstop=8          " Replace 8 spaces with a tab
   autocmd FileType sgml set autoindent         " Automatic indentation
 augroup END

     --------------------------------------------------------------

  10.1.4 Tag Style

    10.1.4.1 Tag Spacing

   Tags that start at the same indent as a previous tag should be
   separated by a blank line, and those that are not at the same
   indent as a previous tag should not:

 <article lang='en'>
   <articleinfo>
     <title>NIS</title>

     <pubdate>October 1999</pubdate>

     <abstract>
       <para>...
         ...
         ...</para>
     </abstract>
   </articleinfo>

   <sect1>
     <title>...</title>

     <para>...</para>
   </sect1>

   <sect1>
     <title>...</title>

     <para>...</para>
   </sect1>
 </article>

     --------------------------------------------------------------

    10.1.4.2 Separating Tags

   Tags like <itemizedlist> which will always have further tags
   inside them, and in fact do not take character data themselves,
   are always on a line by themselves.

   Tags like <para> and <term> do not need other tags to contain
   normal character data, and their contents begin immediately after
   the tag, on the same line.

   The same applies to when these two types of tags close.

   This leads to an obvious problem when mixing these tags.

   When a starting tag which cannot contain character data directly
   follows a tag of the type that requires other tags within it to
   use character data, they are on separate lines. The second tag
   should be properly indented.

   When a tag which can contain character data closes directly after
   a tag which cannot contain character data closes, they co-exist on
   the same line.

     --------------------------------------------------------------

  10.1.5 White Space Changes

   When committing changes, do not commit changes to the content at
   the same time as changes to the formatting.

   This is so that the teams that convert the documentation to other
   languages can quickly see what content has actually changed in
   your commit, without having to decide whether a line has changed
   because of the content, or just because it has been refilled.

   For example, if you have added two sentences to a paragraph, such
   that the line lengths on the paragraph now go over 80 columns,
   first commit your change with the too-long line lengths. Then fix
   the line wrapping, and commit this second change. In the commit
   message for the second change, be sure to indicate that this is a
   whitespace-only change, and that the translation team can ignore
   it.

     --------------------------------------------------------------

  10.1.6 Non-Breaking Space

   Avoid line breaks in places where they look ugly or make it
   difficult to follow a sentence. Line breaks depend on the width of
   the chosen output medium. In particular, viewing the HTML
   documentation with a text browser can lead to badly formatted
   paragraphs like the next one:

 Data capacity ranges from 40 MB to 15
 GB.  Hardware compression ...

   The general entity &nbsp; prohibits line breaks between parts
   belonging together. Use non-breaking spaces in the following
   places:

     * between numbers and units:

 57600&nbsp;bps

     * between program names and version numbers:

 FreeBSD&nbsp;4.7

     * between multiword names (use with caution when applying this
       to more than 3-4 word names like "The FreeBSD Brazilian
       Portuguese Documentation Project"):

 Sun&nbsp;Microsystems

     --------------------------------------------------------------

10.2 Word List

   The following is a small list of words spelled the way they should
   be used in the FreeBSD Documentation Project. If the word you are
   looking for is not in this list, then please consult the O'Reilly
   word list.

     * 2.2.X

     * 4.X-STABLE

     * CD-ROM

     * DoS (Denial of Service)

     * Ports Collection

     * IPsec

     * Internet

     * MHz

     * Soft Updates

     * Unix

     * disk label

     * email

     * file system

     * manual page

     * mail server

     * name server

     * null-modem

     * web server

     --------------------------------------------------------------

                 Chapter 11 Using sgml-mode with Emacs

   Recent versions of Emacs or XEmacs (available from the Ports
   Collection) contain a very useful package called PSGML (can be
   installed from editors/psgml). Automatically invoked when a file
   with the .xml extension is loaded, or by typing M-x sgml-mode, it
   is a major mode for dealing with SGML files, elements and
   attributes.

   An understanding of some of the commands provided by this mode can
   make working with SGML documents such as the Handbook much easier.

   C-c C-e

           Runs sgml-insert-element. You will be prompted for the
           name of the element to insert at the current point. You
           can use the Tab key to complete the element. Elements that
           are not valid at the current point will be disallowed.

           The start and end tags for the element will be inserted.
           If the element contains other, mandatory, elements then
           these will be inserted as well.

   C-c =

           Runs sgml-change-element-name. Place the point within an
           element and run this command. You will be prompted for the
           name of the element to change to. Both the start and end
           tags of the current element will be changed to the new
           element.

   C-c C-r

           Runs sgml-tag-region. Select some text (move to start of
           text, C-space, move to end of text, C-space) and then run
           this command. You will be prompted for the element to use.
           This element will then be inserted immediately before and
           after your marked region.

   C-c -

           Runs sgml-untag-element. Place the point within the start
           or end tag of an element you want to remove, and run this
           command. The element's start and end tags will be removed.

   C-c C-q

           Runs sgml-fill-element. Will recursively fill (i.e.,
           reformat) content from the current element in. The filling
           will affect content in which whitespace is significant,
           such as within <programlisting> elements, so run this
           command with care.

   C-c C-a

           Runs sgml-edit-attributes. Opens a second buffer
           containing a list of all the attributes for the closest
           enclosing element, and their current values. Use Tab to
           navigate between attributes, C-k to remove an existing
           value and replace it with a new one, C-c C-c to close this
           buffer and return to the main document.

   C-c C-v

           Runs sgml-validate. Prompts you to save the current
           document (if necessary) and then runs an SGML validator.
           The output from the validator is captured into a new
           buffer, and you can then navigate from one troublespot to
           the next, fixing markup errors as you go.

   C-c /

           Runs sgml-insert-end-tag. Inserts the end tag for the
           current open element.

   Doubtless there are other useful functions of this mode, but those
   are the ones I use most often.

   You can also use the following entries in .emacs to set proper
   spacing, indentation, and column width for working with the
   Documentation Project.

     (defun local-sgml-mode-hook
       (setq fill-column 70
             indent-tabs-mode nil
             next-line-add-newlines nil
             standard-indent 4
             sgml-indent-data t)
       (auto-fill-mode t)
       (setq sgml-catalog-files '("/usr/local/share/xml/catalog")))
     (add-hook 'psgml-mode-hook
       '(lambda () (local-psgml-mode-hook)))

     --------------------------------------------------------------

                          Chapter 12 See Also

   This document is deliberately not an exhaustive discussion of XML,
   the DTDs listed, and the FreeBSD Documentation Project. For more
   information about these, you are encouraged to see the following
   web sites.

     --------------------------------------------------------------

12.1 The FreeBSD Documentation Project

     * The FreeBSD Documentation Project web pages

     * The FreeBSD Handbook

     --------------------------------------------------------------

12.2 XML

     * W3C's XML page SGML/XML web page

     --------------------------------------------------------------

12.3 HTML

     * The World Wide Web Consortium

     * The HTML 4.0 specification

     --------------------------------------------------------------

12.4 DocBook

     * The DocBook Technical Committee, maintainers of the DocBook
       DTD

     * DocBook: The Definitive Guide, the online documentation for
       the DocBook DTD

     * The DocBook Open Repository contains DSSSL stylesheets and
       other resources for people using DocBook

     --------------------------------------------------------------

12.5 The Linux Documentation Project

     * The Linux Documentation Project web pages

     --------------------------------------------------------------

                          Appendix A. Examples

   This appendix contains example XML files and command lines you can
   use to convert them from one output format to another. If you have
   successfully installed the Documentation Project tools then you
   should be able to use these examples directly.

   These examples are not exhaustive-they do not contain all the
   elements you might want to use, particularly in your document's
   front matter. For more examples of DocBook markup you should
   examine the XML source for this and other documents, available in
   the svn doc repository, or available online starting at
   http://svnweb.FreeBSD.org/doc/.

   To avoid confusion, these examples use the standard DocBook 4.1
   DTD rather than the FreeBSD extension. They also use the stock
   stylesheets distributed by Norm Walsh, rather than any
   customizations made to those stylesheets by the FreeBSD
   Documentation Project. This makes them more useful as generic
   DocBook examples.

     --------------------------------------------------------------

A.1 DocBook <book>

   Example A-1. DocBook <book>

 <!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
   "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">

 <book lang='en'>
   <bookinfo>
     <title>An Example Book</title>

     <author>
       <firstname>Your first name</firstname>
       <surname>Your surname</surname>
       <affiliation>
         <address><email>foo@example.com</email></address>
       </affiliation>
     </author>

     <copyright>
       <year>2000</year>
       <holder>Copyright string here</holder>
     </copyright>

     <abstract>
       <para>If your book has an abstract then it should go here.</para>
     </abstract>
   </bookinfo>

   <preface>
     <title>Preface</title>

     <para>Your book may have a preface, in which case it should be placed
       here.</para>
   </preface>

   <chapter>
     <title>My First Chapter</title>

     <para>This is the first chapter in my book.</para>

     <sect1>
       <title>My First Section</title>

       <para>This is the first section in my book.</para>
     </sect1>
   </chapter>
 </book>

     --------------------------------------------------------------

A.2 DocBook <article>

   Example A-2. DocBook <article>

 <!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
   "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">

 <article lang='en'>
   <articleinfo>
     <title>An Example Article</title>

     <author>
       <firstname>Your first name</firstname>
       <surname>Your surname</surname>
       <affiliation>
         <address><email>foo@example.com</email></address>
       </affiliation>
     </author>

     <copyright>
       <year>2000</year>
       <holder>Copyright string here</holder>
     </copyright>

     <abstract>
       <para>If your article has an abstract then it should go here.</para>
     </abstract>
   </articleinfo>

   <sect1>
     <title>My First Section</title>

     <para>This is the first section in my article.</para>

     <sect2>
       <title>My First Sub-Section</title>

       <para>This is the first sub-section in my article.</para>
     </sect2>
   </sect1>
 </article>

     --------------------------------------------------------------

A.3 Producing Formatted Output

   This section assumes that you have installed the software listed
   in the textproc/docproj port, either by hand, or by using the
   port. Further, it is assumed that your software is installed in
   subdirectories under /usr/local/, and the directory where binaries
   have been installed is in your PATH. Adjust the paths as necessary
   for your system.

     --------------------------------------------------------------

  A.3.1 Using Jade

   Example A-3. Converting DocBook to HTML (One Large File)

 % jade -V nochunks \  (1)
     -c /usr/local/share/xml/docbook/dsssl/modular/catalog \ (2)
     -c /usr/local/share/xml/docbook/catalog \
     -c /usr/local/share/xml/jade/catalog \
     -d /usr/local/share/xml/docbook/dsssl/modular/html/docbook.dsl \(3)
     -t sgml (4) file.xml > file.html (5)

   (1)
           Specifies the nochunks parameter to the stylesheets,
           forcing all output to be written to the standard output
           (using Norm Walsh's stylesheets).
   (2)
           Specifies the catalogs that Jade will need to process.
           Three catalogs are required. The first is a catalog that
           contains information about the DSSSL stylesheets. The
           second contains information about the DocBook DTD. The
           third contains information specific to Jade.
   (3)
           Specifies the full path to the DSSSL stylesheet that Jade
           will use when processing the document.
   (4)
           Instructs Jade to perform a transformation from one DTD to
           another. In this case, the input is being transformed from
           the DocBook DTD to the HTML DTD.
   (5)
           Specifies the file that Jade should process, and redirects
           output to the specified .html file.

   Example A-4. Converting DocBook to HTML (Several Small Files)

 % jade \
     -c /usr/local/share/xml/docbook/dsssl/modular/catalog \ (1)
     -c /usr/local/share/xml/docbook/catalog \
     -c /usr/local/share/xml/jade/catalog \
     -d /usr/local/share/xml/docbook/dsssl/modular/html/docbook.dsl \(2)
     -t sgml (3) file.xml (4)

   (1)
           Specifies the catalogs that Jade will need to process.
           Three catalogs are required. The first is a catalog that
           contains information about the DSSSL stylesheets. The
           second contains information about the DocBook DTD. The
           third contains information specific to Jade.
   (2)
           Specifies the full path to the DSSSL stylesheet that Jade
           will use when processing the document.
   (3)
           Instructs Jade to perform a transformation from one DTD to
           another. In this case, the input is being transformed from
           the DocBook DTD to the HTML DTD.
   (4)
           Specifies the file that Jade should process. The
           stylesheets determine how the individual HTML files will
           be named, and the name of the "root" file (i.e., the one
           that contains the start of the document.

   This example may still only generate one HTML file, depending on
   the structure of the document you are processing, and the
   stylesheet's rules for splitting output.

   Example A-5. Converting DocBook to Postscript

   The source XML file must be converted to a TeX file.

 % jade -V tex-backend \ (1)
     -c /usr/local/share/xml/docbook/dsssl/modular/catalog \ (2)
     -c /usr/local/share/xml/docbook/catalog \
     -c /usr/local/share/xml/jade/catalog \
     -d /usr/local/share/xml/docbook/dsssl/modular/print/docbook.dsl \(3)
     -t tex (4) file.xml

   (1)
           Customizes the stylesheets to use various options specific
           to producing output for TeX.
   (2)
           Specifies the catalogs that Jade will need to process.
           Three catalogs are required. The first is a catalog that
           contains information about the DSSSL stylesheets. The
           second contains information about the DocBook DTD. The
           third contains information specific to Jade.
   (3)
           Specifies the full path to the DSSSL stylesheet that Jade
           will use when processing the document.
   (4)
           Instructs Jade to convert the output to TeX.

   The generated .tex file must now be run through tex, specifying
   the &jadetex macro package.

 % tex "&jadetex" file.tex

   You have to run tex at least three times. The first run processes
   the document, and determines areas of the document which are
   referenced from other parts of the document, for use in indexing,
   and so on.

   Do not be alarmed if you see warning messages such as "LaTeX
   Warning: Reference `136' on page 5 undefined on input line 728."
   at this point.

   The second run reprocesses the document now that certain pieces of
   information are known (such as the document's page length). This
   allows index entries and other cross-references to be fixed up.

   The third pass performs any final cleanup necessary.

   The output from this stage will be file.dvi.

   Finally, run dvips to convert the .dvi file to Postscript.

 % dvips -o file.ps file.dvi

   Example A-6. Converting DocBook to PDF

   The first part of this process is identical to that when
   converting DocBook to Postscript, using the same jade command line
   (Example A-5).

   When the .tex file has been generated you run pdfTeX. However, use
   the &pdfjadetex macro package instead.

 % pdftex "&pdfjadetex" file.tex

   Again, run this command three times.

   This will generate file.pdf, which does not need to be processed
   any further.

  Notes

   [1] Parameter entities use the Percent symbol.                     
   [2] A short history can be found under                             
       http://www.oasis-open.org/docbook/intro.shtml#d0e41.           
   [3] There are other types of list element in DocBook, but we are   
       not concerned with those at the moment.                        

     --------------------------------------------------------------
