/**
 * @file    createExampleSBML.cpp
 * @brief   Creates example SBML models presented in the SBML specification.
 * @author  Akiya Jouraku
 * @author  Michael Hucka
 * @author  Sarah Keating
 *
 * $Id: createExampleSBML.cpp 8892 2009-01-18 17:36:56Z ajouraku $
 * $HeadURL: https://sbml.svn.sourceforge.net/svnroot/sbml/trunk/libsbml/examples/c++/createExampleSBML.cpp $
 *
 * This file is part of libSBML.  Please visit http://sbml.org for more
 * information about SBML, and the latest version of libSBML.
 */

#include <iostream>
#include <sbml/SBMLTypes.h>

using namespace std;

//
// Functions for creating the Example SBML documents.
//
SBMLDocument* createExampleEnzymaticReaction();            /* 7.1 */
SBMLDocument* createExampleInvolvingUnits();               /* 7.2 */
SBMLDocument* createExampleInvolvingFunctionDefinitions(); /* 7.8 */

//
// Helper functions for validating and writing the SBML documents created.
//
bool validateExampleSBML(SBMLDocument *sbmlDoc);
bool writeExampleSBML(const SBMLDocument *sbmlDoc, const string& filename);

//
// These variables are used in writeExampleSBML when writing an SBML
// document.  They are handed to libSBML functions in order to include
// the program information into comments within the SBML file.
//
const static string ProgramName    = "createExampleModels";
const static string ProgramVersion = "1.0.0";

//
// The SBML Level and Version of the example SBML models.
//
const static unsigned int Level   = 2;
const static unsigned int Version = 4;


//===============================================================================
//
// Main routine
//
//  Creates SBML models represented in "Example models expressed in XML using
//  SBML" in Section 7 of the SBML Level 2 Version 4 specification(*). 
//
//   (*) The specification document is available at the following URL:
//       http://sbml.org/Documents/Specifications
//
//===============================================================================
//
int
main (int argc, char *argv[])
{
  SBMLDocument* sbmlDoc = 0;
  bool SBMLok           = false;

  try
  {
    //-------------------------------------------------
    // 7.1 A Simple example application of SBML
    //-------------------------------------------------

    sbmlDoc = createExampleEnzymaticReaction(); 
    SBMLok  = validateExampleSBML(sbmlDoc);
    if (SBMLok) writeExampleSBML(sbmlDoc, "enzymaticreaction.xml");
    delete sbmlDoc;
    if (!SBMLok) return 1;

    //-------------------------------------------------
    // 7.2 Example involving units
    //-------------------------------------------------

    sbmlDoc = createExampleInvolvingUnits(); 
    SBMLok  = validateExampleSBML(sbmlDoc);
    if (SBMLok) writeExampleSBML(sbmlDoc, "units.xml");
    delete sbmlDoc;
    if (!SBMLok) return 1;

    //-------------------------------------------------
    // 7.8 Example involving function definitions
    //-------------------------------------------------

    sbmlDoc = createExampleInvolvingFunctionDefinitions(); 
    SBMLok  = validateExampleSBML(sbmlDoc);
    if (SBMLok) writeExampleSBML(sbmlDoc, "functiondef.xml");
    delete sbmlDoc;
    if (!SBMLok) return 1;

  }
  catch (std::bad_alloc& e)
  {
    cerr << e.what() << ": Unable to allocate memory." << endl;
    return 1;
  }
  catch (...)
  {
    cerr << "Unexpected exceptional condition encountered." << endl;
    return 1;
  }

  // A 0 return status is the standard Unix/Linux way to say "all ok".
  return 0;

}


//===============================================================================
//
//
// Functions for creating the Example SBML documents.
//
//
//===============================================================================


/**
 *
 * Creates an SBML model represented in "7.1 A Simple example application of SBML"
 * in the SBML Level 2 Version 4 Specification.
 *
 */
SBMLDocument* createExampleEnzymaticReaction()
{
  const unsigned int level   = Level;
  const unsigned int version = Version;

  //---------------------------------------------------------------------------
  //
  // Creates an SBMLDocument object 
  //
  //---------------------------------------------------------------------------

  SBMLDocument* sbmlDoc = new SBMLDocument(level,version);

  //---------------------------------------------------------------------------
  //
  // Creates a Model object inside the SBMLDocument object. 
  //
  //---------------------------------------------------------------------------

  Model* model = sbmlDoc->createModel();
  model->setId("EnzymaticReaction");

  //---------------------------------------------------------------------------
  //
  // Creates UnitDefinition objects inside the Model object.
  //
  //---------------------------------------------------------------------------

  // Temporary pointers (reused more than once below).

  UnitDefinition* unitdef;
  Unit* unit;

  //---------------------------------------------------------------------------  
  // (UnitDefinition1) Creates an UnitDefinition object ("per_second")
  //---------------------------------------------------------------------------

  unitdef = model->createUnitDefinition();
  unitdef->setId("per_second");

  //  Creates an Unit inside the UnitDefinition object 

  unit = unitdef->createUnit();
  unit->setKind(UNIT_KIND_SECOND);
  unit->setExponent(-1);

  //--------------------------------------------------------------------------------
  // (UnitDefinition2) Creates an UnitDefinition object ("litre_per_mole_per_second") 
  //--------------------------------------------------------------------------------
    
  // Note that we can reuse the pointers 'unitdef' and 'unit' because the
  // actual UnitDefinition object (along with the Unit objects within it)
  // is already attached to the Model object.

  unitdef = model->createUnitDefinition();
  unitdef->setId("litre_per_mole_per_second");
    
  //  Creates an Unit inside the UnitDefinition object ("litre_per_mole_per_second")

  unit = unitdef->createUnit();
  unit->setKind(UNIT_KIND_MOLE);
  unit->setExponent(-1);

  //  Creates an Unit inside the UnitDefinition object ("litre_per_mole_per_second")

  unit = unitdef->createUnit();
  unit->setKind(UNIT_KIND_LITRE);
  unit->setExponent(1);

  //  Creates an Unit inside the UnitDefinition object ("litre_per_mole_per_second")

  unit = unitdef->createUnit();
  unit->setKind(UNIT_KIND_SECOND);
  unit->setExponent(-1);


  //---------------------------------------------------------------------------
  //
  // Creates a Compartment object inside the Model object. 
  //
  //---------------------------------------------------------------------------

  Compartment* comp;
  const string compName = "cytosol";

  // Creates a Compartment object ("cytosol")

  comp = model->createCompartment();
  comp->setId(compName);
 
  // Sets the "size" attribute of the Compartment object.
  //
  // We are not setting the units on the compartment size explicitly, so
  // the units of this Compartment object will be the default SBML units of
  // volume, which are liters.
  //
  comp->setSize(1e-14);


  //---------------------------------------------------------------------------
  //
  // Creates Species objects inside the Model object. 
  //
  //---------------------------------------------------------------------------
  
  // Temporary pointer (reused more than once below).
  
  Species *sp;

  //---------------------------------------------------------------------------
  // (Species1) Creates a Species object ("ES")
  //---------------------------------------------------------------------------

  // Create the Species objects inside the Model object. 

  sp = model->createSpecies();
  sp->setId("ES");
  sp->setName("ES");

  // Sets the "compartment" attribute of the Species object to identify the 
  // compartment in which the Species object is located.

  sp->setCompartment(compName);

  // Sets the "initialAmount" attribute of the Species object.
  //
  //  In SBML, the units of a Species object's initial quantity are
  //  determined by two attributes, "substanceUnits" and
  //  "hasOnlySubstanceUnits", and the "spatialDimensions" attribute
  //  of the Compartment object ("cytosol") in which the species
  //  object is located.  Here, we are using the default values for
  //  "substanceUnits" (which is "mole") and "hasOnlySubstanceUnits"
  //  (which is "false").  The compartment in which the species is
  //  located uses volume units of liters, so the units of these
  //  species (when the species appear in numerical formulas in the
  //  model) will be moles/liters.  
  //
  sp->setInitialAmount(0);

  //---------------------------------------------------------------------------
  // (Species2) Creates a Species object ("P")
  //---------------------------------------------------------------------------

  sp = model->createSpecies();
  sp->setCompartment(compName);
  sp->setId("P");
  sp->setName("P");
  sp->setInitialAmount(0);

  //---------------------------------------------------------------------------
  // (Species3) Creates a Species object ("S")
  //---------------------------------------------------------------------------

  sp = model->createSpecies();
  sp->setCompartment(compName);
  sp->setId("S");
  sp->setName("S");
  sp->setInitialAmount(1e-20);

  //---------------------------------------------------------------------------
  // (Species4) Creates a Species object ("E")
  //---------------------------------------------------------------------------

  sp = model->createSpecies();
  sp->setCompartment(compName);
  sp->setId("E");
  sp->setName("E");
  sp->setInitialAmount(5e-21);

  
  //---------------------------------------------------------------------------
  //
  // Creates Reaction objects inside the Model object. 
  //
  //---------------------------------------------------------------------------
  
  // Temporary pointers.

  Reaction* reaction;
  SpeciesReference* spr;
  KineticLaw* kl;

  //---------------------------------------------------------------------------
  // (Reaction1) Creates a Reaction object ("veq").
  //---------------------------------------------------------------------------

  reaction = model->createReaction();
  reaction->setId("veq");

  // (Reactant1) Creates a Reactant object that references Species "E"
  // in the model.  The object will be created within the reaction in the
  // SBML <listOfReactants>.

  spr = reaction->createReactant();
  spr->setSpecies("E");

  // (Reactant2) Creates a Reactant object that references Species "S"
  // in the model.

  spr = reaction->createReactant();
  spr->setSpecies("S");

  //---------------------------------------------------------------------------
  // (Product1) Creates a Product object that references Species "ES" in
  // the model.
  //---------------------------------------------------------------------------

  spr = reaction->createProduct();
  spr->setSpecies("ES");

  //---------------------------------------------------------------------------
  // Creates a KineticLaw object inside the Reaction object ("veq"). 
  //---------------------------------------------------------------------------

  kl = reaction->createKineticLaw();

 //---------------------------------------------------------------------------
   // Creates an ASTNode object which represents the following math of the
   // KineticLaw.
   //
   //      <math xmlns="http://www.w3.org/1998/Math/MathML">
   //        <apply>
   //          <times/>
   //          <ci> cytosol </ci>
   //          <apply>
   //            <minus/>
   //            <apply>
   //              <times/>
   //              <ci> kon </ci>
   //              <ci> E </ci>
   //              <ci> S </ci>
   //            </apply>
   //            <apply>
   //              <times/>
   //              <ci> koff </ci>
   //              <ci> ES </ci>
   //            </apply>
   //          </apply>
   //        </apply>
   //      </math>
   //
 //---------------------------------------------------------------------------

   //------------------------------------------
   //
   // create nodes representing the variables
   //
   //------------------------------------------

   ASTNode* astCytosol = new ASTNode(AST_NAME);
   astCytosol->setName("cytosol");

   ASTNode* astKon = new ASTNode(AST_NAME);
   astKon->setName("kon");

   ASTNode* astKoff = new ASTNode(AST_NAME);
   astKoff->setName("koff");

   ASTNode* astE = new ASTNode(AST_NAME);
   astE->setName("E");

   ASTNode* astS = new ASTNode(AST_NAME);
   astS->setName("S");

   ASTNode* astES = new ASTNode(AST_NAME);
   astES->setName("ES");


   //--------------------------------------------
   //
   // create node representing
   //            <apply>
   //              <times/>
   //              <ci> koff </ci>
   //              <ci> ES </ci>
   //            </apply>
   //
   //--------------------------------------------

   ASTNode *astTimes1 = new ASTNode(AST_TIMES);
   astTimes1->addChild(astKoff);
   astTimes1->addChild(astES);

   //--------------------------------------------
   //
   // create node representing
   //            <apply>
   //              <times/>
   //              <ci> kon </ci>
   //              <ci> E </ci>
   //              <ci> S </ci>
   //            </apply>
   //
   //
   // (NOTES)
   //
   //  Since there is a restriction with an ASTNode of "<times/>" operation
   //  such that the ASTNode is a binary class and thus only two operands can
   //  be directly added, the following code in this comment block is invalid
   //  because the code directly adds three <ci> ASTNodes to <times/> ASTNode.
   //
   //    ASTNode *astTimes = new ASTNode(AST_TIMES);
   //    astTimes->addChild(astKon);
   //    astTimes->addChild(astE);
   //    astTimes->addChild(astS);
   //
   // The following valid code after this comment block creates the ASTNode
   // as a binary tree.
   //
   // Please see "Converting between ASTs and text strings" described
   // at http://sbml.org/Software/libSBML/docs/cpp-api/class_a_s_t_node.html
   // for the detailed information.
   //
   //--------------------------------------------

   ASTNode *astTimes2 = new ASTNode(AST_TIMES);
   astTimes2->addChild(astE);
   astTimes2->addChild(astS);

   ASTNode *astTimes = new ASTNode(AST_TIMES);
   astTimes->addChild(astKon);
   astTimes->addChild(astTimes2);

   //--------------------------------------------
   //
   // create node representing
   //          <apply>
   //            <minus/>
   //            <apply>
   //              <times/>
   //              <ci> kon </ci>
   //              <ci> E </ci>
   //              <ci> S </ci>
   //            </apply>
   //            <apply>
   //              <times/>
   //              <ci> koff </ci>
   //              <ci> ES </ci>
   //            </apply>
   //          </apply>
   //
   //--------------------------------------------

   ASTNode *astMinus = new ASTNode(AST_MINUS);
   astMinus->addChild(astTimes);
   astMinus->addChild(astTimes1);


   //--------------------------------------------
   //
   // create node representing
   //        <apply>
   //          <times/>
   //          <ci> cytosol </ci>
   //          <apply>
   //            <minus/>
   //            <apply>
   //              <times/>
   //              <ci> kon </ci>
   //              <ci> E </ci>
   //              <ci> S </ci>
   //            </apply>
   //            <apply>
   //              <times/>
   //              <ci> koff </ci>
   //              <ci> ES </ci>
   //            </apply>
   //          </apply>
   //        </apply>
   //
   //--------------------------------------------

   ASTNode* astMath = new ASTNode(AST_TIMES);
   astMath->addChild(astCytosol);
   astMath->addChild(astMinus);

   //---------------------------------------------
   //
   // set the Math element
   //
   //------------------------------------------------

   kl->setMath(astMath);

  // KineticLaw::setMath(const ASTNode*) sets the math of the KineticLaw object
  // to a copy of the given ASTNode, and thus basically the caller should delete 
  // the original ASTNode object if the caller has the ownership of the object to 
  // avoid memory leak.

   delete astMath;


  //---------------------------------------------------------------------------
  // Creates local Parameter objects inside the KineticLaw object.
  //---------------------------------------------------------------------------

  // Creates a Parameter ("kon")

  Parameter* para = kl->createParameter();
  para->setId("kon");
  para->setValue(1000000);
  para->setUnits("litre_per_mole_per_second");

  // Creates a Parameter ("koff")

  para = kl->createParameter();
  para->setId("koff");
  para->setValue(0.2);
  para->setUnits("per_second");


  //---------------------------------------------------------------------------
  // (Reaction2) Creates a Reaction object ("vcat") .
  //---------------------------------------------------------------------------
  
  reaction = model->createReaction();
  reaction->setId("vcat");
  reaction->setReversible(false);

  //---------------------------------------------------------------------------
  // Creates Reactant objects inside the Reaction object ("vcat"). 
  //---------------------------------------------------------------------------

  // (Reactant1) Creates a Reactant object that references Species "ES" in the
  // model.

  spr = reaction->createReactant();
  spr->setSpecies("ES");

  //---------------------------------------------------------------------------
  // Creates a Product object inside the Reaction object ("vcat"). 
  //---------------------------------------------------------------------------
  
  // (Product1) Creates a Product object that references Species "E" in the model.

  spr = reaction->createProduct();
  spr->setSpecies("E");

  // (Product2) Creates a Product object that references Species "P" in the model.

  spr = reaction->createProduct();
  spr->setSpecies("P");

  //---------------------------------------------------------------------------
  // Creates a KineticLaw object inside the Reaction object ("vcat"). 
  //---------------------------------------------------------------------------
  
  kl = reaction->createKineticLaw();

  //---------------------------------------------------------------------------
  // Sets a math (ASTNode object) to the KineticLaw object.
  //---------------------------------------------------------------------------

  // To create mathematical expressions, one would typically construct
  // an ASTNode tree as the above example code which creates a math of another
  // KineticLaw object.  Here, to save some space and illustrate another approach 
  // of doing it, we will write out the formula in MathML form and then use a 
  // libSBML convenience function to create the ASTNode tree for us.  
  // (This is a bit dangerous; it's very easy to make mistakes when writing MathML 
  // by hand, so in a real program, we would not really want to do it this way.)

  string mathXMLString = "<math xmlns=\"http://www.w3.org/1998/Math/MathML\">"
                         "  <apply>"
                         "    <times/>"
                         "    <ci> cytosol </ci>"
                         "    <ci> kcat </ci>"
                         "    <ci> ES </ci>"
                         "  </apply>"
                         "</math>";

  astMath = readMathMLFromString(mathXMLString.c_str());
  kl->setMath(astMath);
  delete astMath;

  //---------------------------------------------------------------------------
  // Creates local Parameter objects inside the KineticLaw object.
  //---------------------------------------------------------------------------

  // Creates a Parameter ("kcat")

  para = kl->createParameter();
  para->setId("kcat");
  para->setValue(0.1);
  para->setUnits("per_second");


  // Returns the created SBMLDocument object.
  // The returned object must be explicitly deleted by the caller,
  // otherwise a memory leak will happen.

  return sbmlDoc;

}


/**
 *
 * Creates an SBML model represented in "7.2 Example involving units"
 * in the SBML Level 2 Version 4 Specification.
 *
 */
SBMLDocument* createExampleInvolvingUnits()
{
  const unsigned int level   = Level;
  const unsigned int version = Version;

  //---------------------------------------------------------------------------
  //
  // Creates an SBMLDocument object 
  //
  //---------------------------------------------------------------------------

  SBMLDocument* sbmlDoc = new SBMLDocument(level,version);

  // Adds the namespace for XHTML to the SBMLDocument object.  We need this
  // because we will add notes to the model.  (By default, the SBML document
  // created by SBMLDocument only declares the SBML XML namespace.)

  sbmlDoc->getNamespaces()->add("http://www.w3.org/1999/xhtml", "xhtml");

  //---------------------------------------------------------------------------
  //
  // Creates a Model object inside the SBMLDocument object. 
  //
  //---------------------------------------------------------------------------

  Model* model = sbmlDoc->createModel();
  model->setId("unitsExample");

  //---------------------------------------------------------------------------
  //
  // Creates UnitDefinition objects inside the Model object.
  //
  //---------------------------------------------------------------------------

  // Temporary pointers (reused more than once below).

  UnitDefinition* unitdef;
  Unit *unit;

  //---------------------------------------------------------------------------  
  // (UnitDefinition1) Creates an UnitDefinition object ("substance").
  //
  // This has the effect of redefining the default unit of subtance for the
  // whole model.
  //---------------------------------------------------------------------------

  unitdef = model->createUnitDefinition();
  unitdef->setId("substance");

  //  Creates an Unit inside the UnitDefinition object 

  unit = unitdef->createUnit();
  unit->setKind(UNIT_KIND_MOLE);
  unit->setScale(-3);

  //--------------------------------------------------------------------------------
  // (UnitDefinition2) Creates an UnitDefinition object ("mmls") 
  //--------------------------------------------------------------------------------
    
  // Note that we can reuse the pointers 'unitdef' and 'unit' because the
  // actual UnitDefinition object (along with the Unit objects within it)
  // is already attached to the Model object.

  unitdef = model->createUnitDefinition();
  unitdef->setId("mmls");
    
  //  Creates an Unit inside the UnitDefinition object ("mmls")

  unit = unitdef->createUnit();
  unit->setKind(UNIT_KIND_MOLE);
  unit->setScale(-3);

  //  Creates an Unit inside the UnitDefinition object ("mmls")

  unit = unitdef->createUnit();
  unit->setKind(UNIT_KIND_LITRE);
  unit->setExponent(-1);

  //  Creates an Unit inside the UnitDefinition object ("mmls")

  unit = unitdef->createUnit();
  unit->setKind(UNIT_KIND_SECOND);
  unit->setExponent(-1);

  //--------------------------------------------------------------------------------
  // (UnitDefinition3) Creates an UnitDefinition object ("mml") 
  //--------------------------------------------------------------------------------
    
  unitdef = model->createUnitDefinition();
  unitdef->setId("mml");
    
  //  Creates an Unit inside the UnitDefinition object ("mml")

  unit = unitdef->createUnit();
  unit->setKind(UNIT_KIND_MOLE);
  unit->setScale(-3);

  //  Creates an Unit inside the UnitDefinition object ("mml")

  unit = unitdef->createUnit();
  unit->setKind(UNIT_KIND_LITRE);
  unit->setExponent(-1);


  //---------------------------------------------------------------------------
  //
  // Creates a Compartment object inside the Model object. 
  //
  //---------------------------------------------------------------------------

  Compartment* comp;
  const string compName = "cell";

  // Creates a Compartment object ("cell")

  comp = model->createCompartment();
  comp->setId(compName);
 
  // Sets the "size" attribute of the Compartment object.
  //
  //   The units of this Compartment object is the default SBML 
  //   units of volume (litre), and thus we don't have to explicitly invoke 
  //   setUnits("litre") function to set the default units.
  //
  comp->setSize(1);


  //---------------------------------------------------------------------------
  //
  // Creates Species objects inside the Model object. 
  //
  //---------------------------------------------------------------------------
  
  // Temporary pointer (reused more than once below).
  
  Species *sp;

  //---------------------------------------------------------------------------
  // (Species1) Creates a Species object ("x0")
  //---------------------------------------------------------------------------

  sp = model->createSpecies();
  sp->setId("x0");

  // Sets the "compartment" attribute of the Species object to identify the 
  // compartnet in which the Species object located.

  sp->setCompartment(compName);

  // Sets the "initialConcentration" attribute of the Species object.
  //
  //  The units of this Species object is determined by two attributes of this 
  //  Species object ("substanceUnits" and "hasOnlySubstanceUnits") and the
  //  "spatialDimensions" attribute of the Compartment object ("cytosol") in which 
  //  this species object is located.
  //  Since the default values are used for "substanceUnits" (substance (mole)) 
  //  and "hasOnlySubstanceUnits" (false) and the value of "spatialDimension" (3) 
  //  is greater than 0, the units of this Species object is  moles/liters . 
  //
  sp->setInitialConcentration(1);

  //---------------------------------------------------------------------------
  // (Species2) Creates a Species object ("x1")
  //---------------------------------------------------------------------------

  sp = model->createSpecies();
  sp->setId("x1");
  sp->setCompartment(compName);
  sp->setInitialConcentration(1);

  //---------------------------------------------------------------------------
  // (Species3) Creates a Species object ("s1")
  //---------------------------------------------------------------------------

  sp = model->createSpecies();
  sp->setCompartment(compName);
  sp->setId("s1");
  sp->setInitialConcentration(1);

  //---------------------------------------------------------------------------
  // (Species4) Creates a Species object ("s2")
  //---------------------------------------------------------------------------

  sp = model->createSpecies();
  sp->setCompartment(compName);
  sp->setId("s2");
  sp->setInitialConcentration(1);

  //---------------------------------------------------------------------------
  //
  // Creates global Parameter objects inside the Model object. 
  //
  //---------------------------------------------------------------------------

  Parameter* para;

  // Creates a Parameter ("vm")  

  para = model->createParameter();
  para->setId("vm");
  para->setValue(2);
  para->setUnits("mmls");

  // Creates a Parameter ("km")  

  para = model->createParameter();
  para->setId("km");
  para->setValue(2);
  para->setUnits("mml");


  //---------------------------------------------------------------------------
  //
  // Creates Reaction objects inside the Model object. 
  //
  //---------------------------------------------------------------------------
  
  // Temporary pointers.

  Reaction* reaction;
  SpeciesReference* spr;
  KineticLaw* kl;

  //---------------------------------------------------------------------------
  // (Reaction1) Creates a Reaction object ("v1").
  //---------------------------------------------------------------------------

  reaction = model->createReaction();
  reaction->setId("v1");

  //---------------------------------------------------------------------------
  // Creates Reactant objects inside the Reaction object ("v1"). 
  //---------------------------------------------------------------------------

  // (Reactant1) Creates a Reactant object that references Species "x0"
  // in the model.

  spr = reaction->createReactant();
  spr->setSpecies("x0");

  //---------------------------------------------------------------------------
  // Creates a Product object inside the Reaction object ("v1"). 
  //---------------------------------------------------------------------------

  // Creates a Product object that references Species "s1" in the model. 

  spr = reaction->createProduct();
  spr->setSpecies("s1");

  //---------------------------------------------------------------------------
  // Creates a KineticLaw object inside the Reaction object ("v1"). 
  //---------------------------------------------------------------------------
  
  kl = reaction->createKineticLaw();

  // Creates a <notes> element in the KineticLaw object.
  // Here we illustrate how to do it using a literal string.  This requires
  // known the required syntax of XHTML and the requirements for SBML <notes>
  // elements.  Later below, we show how to create notes using objects instead
  // of strings.

  string notesString = "<xhtml:p> ((vm * s1)/(km + s1)) * cell </xhtml:p>";
  kl->setNotes(notesString);

  //---------------------------------------------------------------------------
  // Creates an ASTNode object which represents the following KineticLaw object.
  //
  //  <math xmlns=\"http://www.w3.org/1998/Math/MathML\">
  //   <apply>
  //     <times/>
  //     <apply>
  //       <divide/>
  //       <apply>
  //         <times/>
  //           <ci> vm </ci>
  //           <ci> s1 </ci>
  //       </apply>
  //       <apply>
  //         <plus/>
  //           <ci> km </ci>
  //           <ci> s1 </ci>
  //       </apply>
  //     </apply>
  //     <ci> cell </ci>
  //    </apply>
  //  </math>
  //---------------------------------------------------------------------------

  //
  // In the following code, ASTNode objects, which construct an ASTNode tree 
  // of the above math, are created and added in the order of preorder traversal 
  // of the tree (i.e. the order corresponds to the nested structure of the above 
  // MathML elements), and thus the following code maybe a bit more efficient but 
  // maybe a bit difficult to read.
  //

  ASTNode* astMath = new ASTNode(AST_TIMES);

  astMath->addChild(new ASTNode(AST_DIVIDE));
  ASTNode* astDivide = astMath->getLeftChild();

  astDivide->addChild(new ASTNode(AST_TIMES));
  ASTNode* astTimes = astDivide->getLeftChild();

  astTimes->addChild(new ASTNode(AST_NAME));
  astTimes->getLeftChild()->setName("vm");

  astTimes->addChild(new ASTNode(AST_NAME));
  astTimes->getRightChild()->setName("s1");

  astDivide->addChild(new ASTNode(AST_PLUS));
  ASTNode* astPlus = astDivide->getRightChild();

  astPlus->addChild(new ASTNode(AST_NAME));
  astPlus->getLeftChild()->setName("km");

  astPlus->addChild(new ASTNode(AST_NAME));
  astPlus->getRightChild()->setName("s1");


  astMath->addChild(new ASTNode(AST_NAME));
  astMath->getRightChild()->setName("cell");

  //---------------------------------------------
  //
  // set the Math element
  //
  //------------------------------------------------

  kl->setMath(astMath);
  delete astMath;


  //---------------------------------------------------------------------------
  // (Reaction2) Creates a Reaction object ("v2").
  //---------------------------------------------------------------------------

  reaction = model->createReaction();
  reaction->setId("v2");

  //---------------------------------------------------------------------------
  // Creates Reactant objects inside the Reaction object ("v2"). 
  //---------------------------------------------------------------------------

  // (Reactant2) Creates a Reactant object that references Species "s1"
  // in the model.

  spr = reaction->createReactant();
  spr->setSpecies("s1");

  //---------------------------------------------------------------------------
  // Creates a Product object inside the Reaction object ("v2"). 
  //---------------------------------------------------------------------------

  // Creates a Product object that references Species "s2" in the model. 

  spr = reaction->createProduct();
  spr->setSpecies("s2");

  //---------------------------------------------------------------------------
  // Creates a KineticLaw object inside the Reaction object ("v2"). 
  //---------------------------------------------------------------------------
  
  kl = reaction->createKineticLaw();

  // Sets a notes (by XMLNode) to the KineticLaw object.
  //
  // The following code is an alternative to using setNotes(const string&).
  // The equivalent code would be like this:
  //   
  //     notesString = "<xhtml:p>((vm * s2)/(km + s2))*cell</xhtml:p>";
  //     kl->setNotes(notesString);

  // Creates an XMLNode of start element (<xhtml:p>) without attributes.

  XMLNode notesXMLNode(XMLTriple("p", "", "xhtml"), XMLAttributes());

  // Adds a text element to the start element.

  notesXMLNode.addChild(XMLNode(" ((vm * s2)/(km + s2)) * cell ")); 

  // Adds it to the kineticLaw object.

  kl->setNotes(&notesXMLNode);

  //---------------------------------------------------------------------------
  // Sets a math (ASTNode object) to the KineticLaw object.
  //---------------------------------------------------------------------------

  // To create mathematical expressions, one would typically construct
  // an ASTNode tree as the above example code which creates a math of another
  // KineticLaw object.  Here, to save some space and illustrate another approach 
  // of doing it, we will write out the formula in MathML form and then use a 
  // libSBML convenience function to create the ASTNode tree for us.  
  // (This is a bit dangerous; it's very easy to make mistakes when writing MathML 
  // by hand, so in a real program, we would not really want to do it this way.)

  string mathXMLString = "<math xmlns=\"http://www.w3.org/1998/Math/MathML\">"
                         "  <apply>"
                         "    <times/>"
                         "    <apply>"
                         "      <divide/>"
                         "      <apply>"
                         "        <times/>"
                         "        <ci> vm </ci>"
                         "        <ci> s2 </ci>"
                         "      </apply>"
                         "      <apply>"
                         "        <plus/>"
                         "          <ci> km </ci>"
                         "          <ci> s2 </ci>"
                         "      </apply>"
                         "    </apply>"
                         "    <ci> cell </ci>"
                         "  </apply>"
                         "</math>";

  astMath = readMathMLFromString(mathXMLString.c_str());
  kl->setMath(astMath);
  delete astMath;


  //---------------------------------------------------------------------------
  // (Reaction3) Creates a Reaction object ("v3").
  //---------------------------------------------------------------------------

  reaction = model->createReaction();
  reaction->setId("v3");

  //---------------------------------------------------------------------------
  // Creates Reactant objects inside the Reaction object ("v3"). 
  //---------------------------------------------------------------------------

  // (Reactant2) Creates a Reactant object that references Species "s2"
  // in the model.

  spr = reaction->createReactant();
  spr->setSpecies("s2");

  //---------------------------------------------------------------------------
  // Creates a Product object inside the Reaction object ("v3"). 
  //---------------------------------------------------------------------------

  // Creates a Product object that references Species "x1" in the model. 

  spr = reaction->createProduct();
  spr->setSpecies("x1");


  //---------------------------------------------------------------------------
  // Creates a KineticLaw object inside the Reaction object ("v3"). 
  //---------------------------------------------------------------------------
  
  kl = reaction->createKineticLaw();

  // Sets a notes (by string) to the KineticLaw object.

  notesString = "<xhtml:p> ((vm * x1)/(km + x1)) * cell </xhtml:p>";
  kl->setNotes(notesString);

  //---------------------------------------------------------------------------
  // Sets a math (ASTNode object) to the KineticLaw object.
  //---------------------------------------------------------------------------

  mathXMLString = "<math xmlns=\"http://www.w3.org/1998/Math/MathML\">"
                  "  <apply>"
                  "    <times/>"
                  "    <apply>"
                  "      <divide/>"
                  "      <apply>"
                  "        <times/>"
                  "        <ci> vm </ci>"
                  "        <ci> x1 </ci>"
                  "      </apply>"
                  "      <apply>"
                  "        <plus/>"
                  "          <ci> km </ci>"
                  "          <ci> x1 </ci>"
                  "      </apply>"
                  "    </apply>"
                  "    <ci> cell </ci>"
                  "  </apply>"
                  "</math>";

  astMath = readMathMLFromString(mathXMLString.c_str());
  kl->setMath(astMath);
  delete astMath;


  // Returns the created SBMLDocument object.
  // The returned object must be explicitly deleted by the caller,
  // otherwise memory leak will happen.

  return sbmlDoc;

}



/**
 *
 * Creates an SBML model represented in "7.8 Example involving function definitions"
 * in the SBML Level 2 Version 4 Specification.
 *
 */
SBMLDocument* createExampleInvolvingFunctionDefinitions()
{
  const unsigned int level   = Level;
  const unsigned int version = Version;

  //---------------------------------------------------------------------------
  //
  // Creates an SBMLDocument object 
  //
  //---------------------------------------------------------------------------

  SBMLDocument* sbmlDoc = new SBMLDocument(level,version);

  //---------------------------------------------------------------------------
  //
  // Creates a Model object inside the SBMLDocument object. 
  //
  //---------------------------------------------------------------------------

  Model* model = sbmlDoc->createModel();
  model->setId("functionExample");

  //---------------------------------------------------------------------------
  //
  // Creates a FunctionDefinition object inside the Model object. 
  //
  //---------------------------------------------------------------------------

  FunctionDefinition* fdef = model->createFunctionDefinition();
  fdef->setId("f");

  // Sets a math (ASTNode object) to the FunctionDefinition object.

  string mathXMLString = "<math xmlns=\"http://www.w3.org/1998/Math/MathML\">"
                         "  <lambda>"
                         "    <bvar>"
                         "      <ci> x </ci>"
                         "    </bvar>"
                         "    <apply>"
                         "      <times/>"
                         "      <ci> x </ci>"
                         "      <cn> 2 </cn>"
                         "    </apply>"
                         "  </lambda>"
                         "</math>";

  ASTNode* astMath = readMathMLFromString(mathXMLString.c_str());
  fdef->setMath(astMath);
  delete astMath;


  //---------------------------------------------------------------------------
  //
  // Creates a Compartment object inside the Model object. 
  //
  //---------------------------------------------------------------------------

  Compartment* comp;
  const string compName = "compartmentOne";

  // Creates a Compartment object ("compartmentOne")

  comp = model->createCompartment();
  comp->setId(compName);
 
  // Sets the "size" attribute of the Compartment object.
  //
  //   The units of this Compartment object is the default SBML 
  //   units of volume (litre), and thus we don't have to explicitly invoke 
  //   setUnits("litre") function to set the default units.
  //
  comp->setSize(1);


  //---------------------------------------------------------------------------
  //
  // Creates Species objects inside the Model object. 
  //
  //---------------------------------------------------------------------------
  
  Species* sp;

  //---------------------------------------------------------------------------
  // (Species1) Creates a Species object ("S1")
  //---------------------------------------------------------------------------

  sp = model->createSpecies();
  sp->setId("S1");

  // Sets the "compartment" attribute of the Species object to identify the 
  // compartnet in which the Species object located.

  sp->setCompartment(compName);

  // Sets the "initialConcentration" attribute of the Species object.
  //
  //  The units of this Species object is determined by two attributes of this 
  //  Species object ("substanceUnits" and "hasOnlySubstanceUnits") and the
  //  "spatialDimension" attribute of the Compartment object ("cytosol") in which 
  //  this species object located.
  //  Since the default values are used for "substanceUnits" (substance (mole)) 
  //  and "hasOnlySubstanceUnits" (false) and the value of "spatialDimension" (3) 
  //  is greater than 0, the units of this Species object is  mole/litre . 
  //

  sp->setInitialConcentration(1);

  //---------------------------------------------------------------------------
  // (Species2) Creates a Species object ("S2")
  //---------------------------------------------------------------------------

  sp = model->createSpecies();
  sp->setId("S2");
  sp->setCompartment(compName);
  sp->setInitialConcentration(0);


  //---------------------------------------------------------------------------
  //
  // Creates a global Parameter object inside the Model object. 
  //
  //---------------------------------------------------------------------------

  Parameter* para;

  // Creates a Parameter ("t")  

  para = model->createParameter();
  para->setId("t");
  para->setValue(1);
  para->setUnits("second");


  //---------------------------------------------------------------------------
  //
  // Creates Reaction objects inside the Model object. 
  //
  //---------------------------------------------------------------------------
  
  // Temporary pointers.

  Reaction* reaction;
  SpeciesReference* spr;
  KineticLaw* kl;

  //---------------------------------------------------------------------------
  // (Reaction1) Creates a Reaction object ("reaction_1").
  //---------------------------------------------------------------------------

  reaction = model->createReaction();
  reaction->setId("reaction_1");
  reaction->setReversible(false);

  //---------------------------------------------------------------------------
  // Creates Reactant objects inside the Reaction object ("reaction_1"). 
  //---------------------------------------------------------------------------

  // (Reactant1) Creates a Reactant object that references Species "S1"
  // in the model.

  spr = reaction->createReactant();
  spr->setSpecies("S1");

  //---------------------------------------------------------------------------
  // Creates a Product object inside the Reaction object ("reaction_1"). 
  //---------------------------------------------------------------------------

  // Creates a Product object that references Species "S2" in the model. 

  spr = reaction->createProduct();
  spr->setSpecies("S2");


  //---------------------------------------------------------------------------
  // Creates a KineticLaw object inside the Reaction object ("reaction_1"). 
  //---------------------------------------------------------------------------
  
  kl = reaction->createKineticLaw();

  //---------------------------------------------------------------------------
  // Sets a math (ASTNode object) to the KineticLaw object.
  //---------------------------------------------------------------------------

  mathXMLString = "<math xmlns=\"http://www.w3.org/1998/Math/MathML\">"
                  "  <apply>"
                  "  <divide/>"
                  "    <apply>"
                  "      <times/>"
                  "      <apply>"
                  "        <ci> f </ci>"
                  "        <ci> S1 </ci>"
                  "      </apply>"
                  "      <ci> compartmentOne </ci>"
                  "    </apply>"
                  "    <ci> t </ci>"
                  "  </apply>"
                  "</math>";

  astMath = readMathMLFromString(mathXMLString.c_str());
  kl->setMath(astMath);
  delete astMath;


  // Returns the created SBMLDocument object.
  // The returned object must be explicitly deleted by the caller,
  // otherwise memory leak will happen.

  return sbmlDoc;
}


//===============================================================================
//
//
// Helper functions for writing/validating the given SBML documents.
// 
//
//===============================================================================

/**
 *  
 *  Validates the given SBMLDocument.
 *
 *   This function is based on validateSBML.cpp implemented by
 *   Sarah Keating, Ben Bornstein, and Michael Hucka.
 *
 */
bool validateExampleSBML (SBMLDocument* sbmlDoc)
{
  if (!sbmlDoc)
  {
    cerr << "validateExampleSBML: given a null SBML Document" << endl;
    return false;
  }
 
  string consistencyMessages;
  string validationMessages;
  bool noProblems                  = true;
  unsigned int numCheckFailures       = 0;
  unsigned int numConsistencyErrors   = 0;
  unsigned int numConsistencyWarnings = 0;
  unsigned int numValidationErrors    = 0;
  unsigned int numValidationWarnings  = 0;

  // LibSBML 3.3 is lenient when generating models from scratch using the
  // API for creating objects.  Once the whole model is done and before it
  // gets written out, it's important to check that the whole model is in
  // fact complete, consistent and valid.

  numCheckFailures = sbmlDoc->checkInternalConsistency();
  if ( numCheckFailures > 0 )
  {
    noProblems = false;
    for (unsigned int i = 0; i < numCheckFailures; i++)
    {
      const SBMLError* sbmlErr = sbmlDoc->getError(i);
      if ( sbmlErr->isFatal() || sbmlErr->isError() )
      {
        ++numConsistencyErrors;
      }
      else
      {
        ++numConsistencyWarnings;
      }      
    } 
    ostringstream oss;
    sbmlDoc->printErrors(oss);
    consistencyMessages = oss.str(); 
  }

  // If the internal checks fail, it makes little sense to attempt
  // further validation, because the model may be too compromised to
  // be properly interpreted.

  if (numConsistencyErrors > 0)
  {
    consistencyMessages += "Further validation aborted."; 
  }
  else
  {
    numCheckFailures = sbmlDoc->checkConsistency();
    if ( numCheckFailures > 0 )
    {
      noProblems = false;
      for (unsigned int i = 0; i < numCheckFailures; i++)
      {
        const SBMLError* sbmlErr = sbmlDoc->getError(i);
        if ( sbmlErr->isFatal() || sbmlErr->isError() )
        {
          ++numValidationErrors;
        }
        else
        {
          ++numValidationWarnings;
        }      
      } 
      ostringstream oss;
      sbmlDoc->printErrors(oss);
      validationMessages = oss.str(); 
    }
  }

  if (noProblems)
    return true;
  else
  {
    if (numConsistencyErrors > 0)
    {
      cout << "ERROR: encountered " << numConsistencyErrors 
           << " consistency error" << (numConsistencyErrors == 1 ? "" : "s")
	   << " in model '" << sbmlDoc->getModel()->getId() << "'." << endl;
    }
    if (numConsistencyWarnings > 0)
    {
      cout << "Notice: encountered " << numConsistencyWarnings
           << " consistency warning" << (numConsistencyWarnings == 1 ? "" : "s")
	   << " in model '" << sbmlDoc->getModel()->getId() << "'." << endl;
    }
    cout << endl << consistencyMessages;

    if (numValidationErrors > 0)
    {
      cout << "ERROR: encountered " << numValidationErrors
           << " validation error" << (numValidationErrors == 1 ? "" : "s")
	   << " in model '" << sbmlDoc->getModel()->getId() << "'." << endl;
    }
    if (numValidationWarnings > 0)
    {
      cout << "Notice: encountered " << numValidationWarnings
           << " validation warning" << (numValidationWarnings == 1 ? "" : "s")
	   << " in model '" << sbmlDoc->getModel()->getId() << "'." << endl;
    }
    cout << endl << validationMessages;

    return (numConsistencyErrors == 0 && numValidationErrors == 0);
  }
}


/**
 *
 * Writes the given SBMLDocument to the given file.
 *
 */ 
bool writeExampleSBML(const SBMLDocument* sbmlDoc, const string& filename)
{
  SBMLWriter sbmlWriter;

  bool result = sbmlWriter.writeSBML(sbmlDoc, filename);

  if (result)
  {
    cout << "Wrote file \"" << filename << "\"" << endl;
    return true;
  }
  else
  {
    cerr << "Failed to write \"" << filename << "\"" << endl;
    return false;
  }
}
