example.xml

<?xml version="1.0" encoding="UTF-8"?>
<graphml xmlns="http://graphml.graphdrawing.org/xmlns"  
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xsi:schemaLocation="http://graphml.graphdrawing.org/xmlns 
        http://graphml.graphdrawing.org/xmlns/1.0/graphml.xsd">
  <key id="type" for="node" attr.name="nodetype" attr.type="string" />
  <key id="subPort" for="node" attr.name="subPort" attr.type="boolean">
	<default>false</default>
  </key>
  <graph id="ir1" edgedefault="directed">
    <node id="n0">
      <data key="type">function</data>
	  <graph id="n0:" edgedefault="directed">
		<node id="n0::p0">
			<data key="type">integer</data>
			<data key="subPort">true</data>
		</node>
		<node id="n0::p1">
			<data key="type">integer</data>
			<data key="subPort">true</data>
		</node>
		<node id="n0::p2">
			<data key="type">integer</data>
			<data key="subPort">true</data>
		</node>
		<node id="n0::n0">
			<data key="type">+</data>
			<port name="left" />
			<port name="right" />
			<port name="out" />
		</node>
		<node id="n0::n1">
			<data key="type">*</data>
			<port name="left" />
			<port name="right" />
			<port name="out" />
		</node>
		<edge source="n0::p0" target="n0::n0" targetport="left"/>
		<edge source="n0::p0" target="n0::n1" targetport="right"/>
		<edge source="n0::p1" target="n0::n1" targetport="left"/>
		<edge source="n0::n1" target="n0::n0" sourceport="out" targetport="right"/>
		<edge source="n0::n0" target="p2" sourceport="out"/>
	  </graph>
    </node>
  </graph>
</graphml>