/**
 * @file    createExampleSBML.cpp
 * @brief   Creates example SBML models presented in the SBML specification.
 * @author  Akiya Jouraku
 * @author  Michael Hucka
 * @author  Sarah Keating
 *
 * <!--------------------------------------------------------------------------
 * This sample program is distributed under a different license than the rest
 * of libSBML.  This program uses the open-source MIT license, as follows:
 *
 * Copyright (c) 2013-2017 by the California Institute of Technology
 * (California, USA), the European Bioinformatics Institute (EMBL-EBI, UK)
 * and the University of Heidelberg (Germany), with support from the National
 * Institutes of Health (USA) under grant R01GM070923.  All rights reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 *
 * Neither the name of the California Institute of Technology (Caltech), nor
 * of the European Bioinformatics Institute (EMBL-EBI), nor of the University
 * of Heidelberg, nor the names of any contributors, may be used to endorse
 * or promote products derived from this software without specific prior
 * written permission.
 * ------------------------------------------------------------------------ -->
 */

import org.sbml.libsbml.ASTNode;
import org.sbml.libsbml.Compartment;
import org.sbml.libsbml.FunctionDefinition;
import org.sbml.libsbml.KineticLaw;
import org.sbml.libsbml.Model;
import org.sbml.libsbml.Parameter;
import org.sbml.libsbml.Reaction;
import org.sbml.libsbml.SBMLDocument;
import org.sbml.libsbml.SBMLError;
import org.sbml.libsbml.Species;
import org.sbml.libsbml.SpeciesReference;
import org.sbml.libsbml.Unit;
import org.sbml.libsbml.UnitDefinition;
import org.sbml.libsbml.XMLAttributes;
import org.sbml.libsbml.XMLNode;
import org.sbml.libsbml.XMLTriple;
import org.sbml.libsbml.libsbml;

public class createExampleSBML {

    //
    // 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.
    //
    private static String ProgramName = "createExampleModels";
    private static String ProgramVersion = "1.0.0";

    //
    // The SBML Level and Version of the example SBML models.
    //
    private static int Level = 2;
    private static 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
    //
    // ===============================================================================
    //
    public static void main(String[] args) {
        System.loadLibrary("sbmlj");
        SBMLDocument sbmlDoc = null;
        boolean SBMLok = false;

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

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

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

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

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

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

        } catch (Exception e) {
            System.err.println("Unexpected exceptional condition encountered.");
            System.exit(1);
        }

        // A 0 return status is the standard Unix/Linux way to say "all ok".
        System.exit(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.
     * 
     */

    private static SBMLDocument createExampleEnzymaticReaction() {
        int level = Level;
        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(libsbml.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(libsbml.UNIT_KIND_MOLE);
        unit.setExponent(-1);

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

        unit = unitdef.createUnit();
        unit.setKind(libsbml.UNIT_KIND_LITRE);
        unit.setExponent(1);

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

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

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

        Compartment comp;
        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(libsbml.AST_NAME);
        astCytosol.setName("cytosol");

        ASTNode astKon = new ASTNode(libsbml.AST_NAME);
        astKon.setName("kon");

        ASTNode astKoff = new ASTNode(libsbml.AST_NAME);
        astKoff.setName("koff");

        ASTNode astE = new ASTNode(libsbml.AST_NAME);
        astE.setName("E");

        ASTNode astS = new ASTNode(libsbml.AST_NAME);
        astS.setName("S");

        ASTNode astES = new ASTNode(libsbml.AST_NAME);
        astES.setName("ES");

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

        ASTNode astTimes1 = new ASTNode(libsbml.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(libsbml.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(libsbml.AST_TIMES);
        astTimes2.addChild(astE);
        astTimes2.addChild(astS);

        ASTNode astTimes = new ASTNode(libsbml.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(libsbml.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(libsbml.AST_TIMES);
        astMath.addChild(astCytosol);
        astMath.addChild(astMinus);

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

        kl.setMath(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 = libsbml.readMathMLFromString(mathXMLString);
        kl.setMath(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.
     * 
     */

    private static SBMLDocument createExampleInvolvingUnits() {
        int level = Level;
        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(libsbml.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(libsbml.UNIT_KIND_MOLE);
        unit.setScale(-3);

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

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

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

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

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

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

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

        Compartment comp;
        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(libsbml.AST_TIMES);

        astMath.addChild(new ASTNode(libsbml.AST_DIVIDE));
        ASTNode astDivide = astMath.getLeftChild();

        astDivide.addChild(new ASTNode(libsbml.AST_TIMES));
        ASTNode astTimes = astDivide.getLeftChild();

        astTimes.addChild(new ASTNode(libsbml.AST_NAME));
        astTimes.getLeftChild().setName("vm");

        astTimes.addChild(new ASTNode(libsbml.AST_NAME));
        astTimes.getRightChild().setName("s1");

        astDivide.addChild(new ASTNode(libsbml.AST_PLUS));
        ASTNode astPlus = astDivide.getRightChild();

        astPlus.addChild(new ASTNode(libsbml.AST_NAME));
        astPlus.getLeftChild().setName("km");

        astPlus.addChild(new ASTNode(libsbml.AST_NAME));
        astPlus.getRightChild().setName("s1");

        astMath.addChild(new ASTNode(libsbml.AST_NAME));
        astMath.getRightChild().setName("cell");

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

        kl.setMath(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 = new XMLNode(new XMLTriple("p", "", "xhtml"),
                new XMLAttributes());

        // Adds a text element to the start element.

        notesXMLNode.addChild(new 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 = libsbml.readMathMLFromString(mathXMLString);
        kl.setMath(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 = libsbml.readMathMLFromString(mathXMLString);
        kl.setMath(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.
     * 
     */

    private static SBMLDocument createExampleInvolvingFunctionDefinitions() {
        int level = Level;
        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 = libsbml.readMathMLFromString(mathXMLString);
        fdef.setMath(astMath);

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

        Compartment comp;
        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 = libsbml.readMathMLFromString(mathXMLString);
        kl.setMath(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.
     * 
     */

    private static boolean validateExampleSBML(SBMLDocument sbmlDoc) {
        if (sbmlDoc == null) {
            System.err
                    .println("validateExampleSBML: given a null SBML Document");
            return false;
        }

        String consistencyMessages = "";
        String validationMessages = "";
        boolean noProblems = true;
        int numCheckFailures = 0;
        int numConsistencyErrors = 0;
        int numConsistencyWarnings = 0;
        int numValidationErrors = 0;
        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 = (int) sbmlDoc.checkInternalConsistency();
        if (numCheckFailures > 0) {
            noProblems = false;
            for (int i = 0; i < numCheckFailures; i++) {
                SBMLError sbmlErr = sbmlDoc.getError(i);
                if (sbmlErr.isFatal() || sbmlErr.isError()) {
                    ++numConsistencyErrors;
                } else {
                    ++numConsistencyWarnings;
                }
            }
            
            consistencyMessages = sbmlDoc.getErrorLog().toString();
        }

        // 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 = (int) sbmlDoc.checkConsistency();
            if (numCheckFailures > 0) {
                noProblems = false;
                for (int i = 0; i < numCheckFailures; i++) {
                    SBMLError sbmlErr = sbmlDoc.getError(i);
                    if (sbmlErr.isFatal() || sbmlErr.isError()) {
                        ++numValidationErrors;
                    } else {
                        ++numValidationWarnings;
                    }
                }
                validationMessages = sbmlDoc.getErrorLog().toString();
            }
        }

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

            if (numValidationErrors > 0) {
                System.out.println("ERROR: encountered " + numValidationErrors
                        + " validation error"
                        + (numValidationErrors == 1 ? "" : "s") + " in model '"
                        + sbmlDoc.getModel().getId() + "'.");
            }
            if (numValidationWarnings > 0) {
                System.out.println("Notice: encountered "
                        + numValidationWarnings + " validation warning"
                        + (numValidationWarnings == 1 ? "" : "s")
                        + " in model '" + sbmlDoc.getModel().getId() + "'.");
            }
            System.out.println();
            System.out.println(validationMessages);

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

    /**
     * 
     * Writes the given SBMLDocument to the given file.
     * 
     */
    private static boolean writeExampleSBML(SBMLDocument sbmlDoc,
            String filename) {
        int result = libsbml.writeSBML(sbmlDoc, filename);

        if (result == 1) {
            System.out.println("Wrote file \"" + filename + "\"");
            return true;
        } else {
            System.out.println("Failed to write \"" + filename + "\"");
            return false;
        }
    }
}
