[xml] XSD: key-keyref in recursive elements

[Cédric Coussinet <cedric coussinet nomoseed net>]

Hello, 

On the XML schema validation in libxml2, I wonder about the behavior of key
(key / keyref).

The following example shows three ways to validate the uniqueness of an
attribute (in the example, necessarily unique because a single target
element). The difficulty lies in the recursive elements.

The first two key (valueUnique and valueKeyAlone) validate the document
while the last (valueKey / valueRef) indicates an error. 

On Windows, I used the libxml2 2.7.8 and the version 2.9.1, same result :

xmllint.exe --noout –schema test.xsd test.xml
Element '{http://www.test.org/test}B': More than one match found for
key-sequence ['1'] of keyref '{http://www.test.org/test}valueRef'.
test.xml fails to validate

test.xml
--------
<?xml version="1.0" encoding="UTF-8"?>
<A xmlns="http://www.test.org/test";
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance";
xsi:noNamespaceSchemaLocation="test.xsd">
   <A>
    <B value="1"/>
   </A>
  <B value="1"/>
</A>

test.xsd
--------
<?xml version="1.0" encoding="utf-8"?>
<schema attributeFormDefault="unqualified" elementFormDefault="qualified"
targetNamespace="http://www.test.org/test";
xmlns="http://www.w3.org/2001/XMLSchema";
xmlns:test="http://www.test.org/test";>
  <element name="A">
    <complexType>
      <sequence>
        <element ref="test:A" minOccurs="0" maxOccurs="unbounded"/>
        <element name="B" minOccurs="0" maxOccurs="unbounded">
          <complexType>
            <attribute name="value" type="integer" use="required"/>
          </complexType>
        </element>
      </sequence>
    </complexType>
    <unique name="valueUnique">
      <selector xpath="./test:B"/>
      <field xpath="@value"/>
    </unique>
    <key name="valueKeyAlone">
      <selector xpath="./test:B"/>
      <field xpath="@value"/>
    </key>
    <key name="valueKey">
      <selector xpath="./test:B"/>
      <field xpath="@value"/>
    </key>
    <keyref name="valueRef" refer="test:valueKey">
      <selector xpath="./test:B"/>
      <field xpath="@value"/>
    </keyref>
  </element>
</schema>

Is this normal? 

The answer in this discussion
(http://lists.w3.org/Archives/Public/xmlschema-dev/2005Sep/0057.html) is
still relevant? 

Thanking you in advance,

Best regards,

Cédric Coussinet
http://www.nomoseed.org