    <?xml version="1.0" encoding="UTF-8"?>
    <sbml xmlns="http://www.sbml.org/sbml/level3/version1/core" level="3" version="1"
          xmlns:comp="http://www.sbml.org/sbml/level3/version1/comp/version1" comp:required="true">
      <model>
        <listOfCompartments>
          <compartment id="compartment" spatialDimensions="3" size="1" constant="true">
            <comp:listOfReplacedElements>
              <comp:replacedElement comp:idRef="compartment" comp:submodelRef="A"/>
              <comp:replacedElement comp:idRef="compartment" comp:submodelRef="B"/>
            </comp:listOfReplacedElements>
          </compartment>
        </listOfCompartments>
        <listOfSpecies>
          <species id="S" compartment="compartment" hasOnlySubstanceUnits="false"
                          boundaryCondition="false" constant="false">
            <comp:listOfReplacedElements>
              <comp:replacedElement comp:idRef="S" comp:submodelRef="A"/>
              <comp:replacedElement comp:idRef="S" comp:submodelRef="B"/>
            </comp:listOfReplacedElements>
          </species>
        </listOfSpecies>
        <comp:listOfSubmodels>
          <comp:submodel comp:id="A" comp:modelRef="ExtMod1"/>
          <comp:submodel comp:id="B" comp:modelRef="ExtMod1"/>
        </comp:listOfSubmodels>
      </model>
      <comp:listOfExternalModelDefinitions>
        <comp:externalModelDefinition comp:id="ExtMod1" comp:source="enzyme_model.xml"
                                      comp:modelRef="enzyme"/>
      </comp:listOfExternalModelDefinitions>
    </sbml>