XOM API for Processing XML with Java

[Michael Kay <mike AT saxonica.com>]

The XSD 1.0 rules for fixed/default attributes of type QName are very 
poorly defined, and it's best to avoid using them.

You code should work OK with an XSD 1.1 processor (I think), where the 
rules have been more clearly spelled out.

Michael Kay
Saxonica

On 24/09/2011 22:07, Brian Uri! wrote:
> Hello,
>
> I seem to be hitting a bug, but I can't determine whether it's a bug in XOM
> or just schemas which could be better written. I've pruned down the code and
> schemas to the bare bits needed to reproduce the issue below.
>
> I have a schema which defines an element and has a fixed optional attribute
> from a third-party schema (XLink 1.1):
>
>      <?xml version="1.0" encoding="utf-8"?>
>      <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema";
>          xmlns="urn:buri:bugtest" xmlns:buri="urn:buri:bugtest"
>          xmlns:xlink="http://www.w3.org/1999/xlink";
>          targetNamespace="urn:buri:bugtest" elementFormDefault="qualified"
> attributeFormDefault="qualified">
>
>          <xs:import namespace="http://www.w3.org/1999/xlink";
> schemaLocation="XLink.xsd"/>
>
>          <xs:element name="revision" type="RevisionType" />
>          <xs:complexType name="RevisionType">
>              <xs:simpleContent>
>                  <xs:extension base="xs:string">
>                      <xs:attribute ref="xlink:type" fixed="resource"
> use="optional"/>
>                  </xs:extension>
>              </xs:simpleContent>
>          </xs:complexType>
>      </xs:schema>
>
> The XLink 1.1 schema provides the definition for the xlink:type attribute:
>
>      <?xml version='1.0' encoding='UTF-8'?>
>      <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema";
>          xmlns:xlink="http://www.w3.org/1999/xlink";
>          targetNamespace="http://www.w3.org/1999/xlink";>
>
>          <xs:attribute name="type" type="xlink:typeType" />
>          <xs:simpleType name="typeType">
>              <xs:restriction base="xs:token">
>                  <xs:enumeration value="simple"/>
>                  <xs:enumeration value="extended"/>
>                  <xs:enumeration value="title"/>
>                  <xs:enumeration value="resource"/>
>                  <xs:enumeration value="locator"/>
>                  <xs:enumeration value="arc"/>
>              </xs:restriction>
>          </xs:simpleType>
>      </xs:schema>
>
> When I try to build a Document with the instance below in a file, everything
> works fine:
>
>      <?xml version='1.0' encoding='UTF-8'?>
>      <buri:revision xmlns:xlink="http://www.w3.org/1999/xlink";
> xmlns:buri="urn:buri:bugtest" xlink:type="resource" />
>
> However, if I remove the attribute from the instance, like this:
>
>      <?xml version='1.0' encoding='UTF-8'?>
>      <buri:revision xmlns:xlink="http://www.w3.org/1999/xlink";
> xmlns:buri="urn:buri:bugtest" />
>
> I get this error from XOM:
>
>      nu.xom.ParsingException: Unprefixed attribute type cannot be in default
> namespace http://www.w3.org/1999/xlink
>          at nu.xom.Builder.build(Unknown Source)
>          [...]
>      Caused by: nu.xom.NamespaceConflictException: Unprefixed attribute type
> cannot be in default namespace http://www.w3.org/1999/xlink
>          at nu.xom.Attribute._setNamespace(Unknown Source)
>          at nu.xom.Attribute.<init>(Unknown Source)
>          at nu.xom.NodeFactory.makeAttribute(Unknown Source)
>
> If I understand it correctly, a fixed optional attribute need not exist in
> an instance, but must have the fixed value if it does, so an instance
> without it should still be valid. Since the 2nd instance doesn't even
> mention "type", I'm not sure why XOM would be trying to build a type
> attribute at all.
>
> The environment details:
>      xom 1.2.6
>      xercesImpl 2.9.1
>      xml-apis 1.3.04
>
>      XMLReader: org.apache.xerces.parsers.SAXParser
>          http://xml.org/sax/features/validation=true
>          http://apache.org/xml/features/validation/schema=true
>          http://apache.org/xml/properties/schema/external-schemaLocationpoints
> at the schema file
>
>      Test Code:
>      Builder builder = new Builder(xmlReader, true);
>      builder.build(new FileReader(new File(theInstance)));
>
> Any insights would be appreciated. I'll be glad to provide more details if I
> pruned too much!
>
> Thanks!
> BU
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