<?xml version="1.0"?>
<xs:schema
targetNamespace="urn:test:foo"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns:foo="urn:test:foo"
elementFormDefault="qualified"
attributeFormDefault="qualified">
<xs:element name="Link">
<xs:complexType>
<xs:simpleContent>
<xs:extension base="xs:string">
<xs:attribute name="linkKey" type="xs:string" use="required"/>
</xs:extension>
</xs:simpleContent>
</xs:complexType>
</xs:element>
<!-- -->
<xs:element name="Foo">
<xs:complexType>
<xs:sequence>
<xs:element name="Def">
<xs:complexType>
<xs:sequence>
<xs:element ref="foo:Link"/>
</xs:sequence>
</xs:complexType>
</xs:element>
<xs:element name="Ref">
<xs:complexType>
<xs:attribute name="linkRef" use="required"/>
</xs:complexType>
</xs:element>
</xs:sequence>
</xs:complexType>
<xs:key name="LinkKey">
<xs:selector xpath=".//foo:Link | .//foo:Link"/>
<xs:field xpath="@foo:linkKey"/>
</xs:key>
<xs:keyref name="LinkKeyRef" refer="foo:LinkKey">
<xs:selector xpath=".//foo:Ref"/>
<xs:field xpath="@foo:linkRef"/>
</xs:keyref>
</xs:element>
</xs:schema>