<?xml version="1.0" encoding="UTF-8"?>
<xs:schema 
   targetNamespace="http://graphml.graphdrawing.org/xmlns"
   xmlns="http://graphml.graphdrawing.org/xmlns"  
   xmlns:xlink="http://www.w3.org/1999/xlink"
   xmlns:xs="http://www.w3.org/2001/XMLSchema"
   elementFormDefault="qualified"
   attributeFormDefault="unqualified"
>

<xs:import namespace="http://www.w3.org/1999/xlink"
           schemaLocation="xlink.xsd"/>

<xs:redefine 
    schemaLocation="http://graphml.graphdrawing.org/xmlns/1.0/graphml.xsd">

  <xs:attributeGroup name="node.extra.attrib">
    <xs:attributeGroup ref="node.extra.attrib"/>
    <xs:attribute ref="xlink:href" use="optional"/>
  </xs:attributeGroup>

</xs:redefine>

</xs:schema>