<?xml version="1.0" encoding="UTF-8"?>
<grammar ns="http://www.gexf.net/1.1draft" xmlns="http://relaxng.org/ns/structure/1.0">
  <!-- extension point -->
  <define name="node-content" combine="interleave">
    <interleave>
      <optional>
        <attribute name="pid">
          <ref name="id-type"/>
        </attribute>
      </optional>
      <optional>
        <element name="nodes">
          <ref name="nodes-content"/>
        </element>
      </optional>
      <optional>
        <element name="edges">
          <ref name="edges-content"/>
        </element>
      </optional>
    </interleave>
  </define>
</grammar>

