Before we begin the actual definition, we must set the stage with a few lines as given in the section called “ General SBML Structure ”. The first line tells the parser that we are dealing with an UTF-8 encoded XML file. The line that begins with <sbml will qualify all un-prefixed names using the SBML URI given in the xmlns attribute. The additional attributes state that we are dealing with level 2 ,version 4 of SBML. The model element type, or tag, marks the beginning of the model.

<?xml version="1.0" encoding="UTF-8"?>
<sbml xmlns="http://www.sbml.org/sbml/level2/version4" level="2" version="4">
<model name="MesoRD Tutorial System">
    

Now we can begin the model definition. To prepare for what will come, we will define a few units which will be useful in later definitions.

<listOfUnitDefinitions>

  <unitDefinition id="um">
    <listOfUnits>
      <unit kind="metre" scale="-6"/>
    </listOfUnits>
  </unitDefinition>

  <unitDefinition id="pMps">
    <listOfUnits>
      <unit kind="mole" exponent="-1"/>
      <unit kind="litre" exponent="+1"/>
      <unit kind="second" exponent="-1"/>
    </listOfUnits>
  </unitDefinition>

  <unitDefinition id="cm2ps">
    <listOfUnits >
      <unit kind="metre" exponent="2" scale="-2"/>
      <unit kind="second" exponent="-1"/>
    </listOfUnits>
  </unitDefinition>

  <unitDefinition id="ps">
    <listOfUnits>
      <unit kind="second" exponent="-1"/>
    </listOfUnits>
  </unitDefinition>
</listOfUnitDefinitions>
    

The above lines define four units.