 <p>There is a schema describing such graph: see <a href="http://graphml.graphdrawing.org/primer/graphml-primer.html" rel="nofollow noreferrer">GraphML</a></p> <p>Example:</p> <pre><code>&lt;?xml version="1.0" encoding="UTF-8"?&gt; &lt;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"&gt; &lt;graph id="G" edgedefault="undirected"&gt; &lt;node id="n0"/&gt; &lt;node id="n1"/&gt; &lt;node id="n2"/&gt; &lt;node id="n3"/&gt; &lt;node id="n4"/&gt; &lt;node id="n5"/&gt; &lt;node id="n6"/&gt; &lt;node id="n7"/&gt; &lt;node id="n8"/&gt; &lt;node id="n9"/&gt; &lt;node id="n10"/&gt; &lt;edge source="n0" target="n2"/&gt; &lt;edge source="n1" target="n2"/&gt; &lt;edge source="n2" target="n3"/&gt; &lt;edge source="n3" target="n5"/&gt; &lt;edge source="n3" target="n4"/&gt; &lt;edge source="n4" target="n6"/&gt; &lt;edge source="n6" target="n5"/&gt; &lt;edge source="n5" target="n7"/&gt; &lt;edge source="n6" target="n8"/&gt; &lt;edge source="n8" target="n7"/&gt; &lt;edge source="n8" target="n9"/&gt; &lt;edge source="n8" target="n10"/&gt; &lt;/graph&gt; &lt;/graphml&gt; </code></pre>