While old gray XPath 1.0 supports only DTD-determined IDs, XPointer Framework also supports schema-determined IDs - an element in XML document can be identified by a value of an attribute or even child element, whose type is xs:ID. I've been implementing support for schema-determined IDs for the XPointer.NET/XInclude.NET library (has no online presence currently after gotdotnet's workspace crashed and I moved the code to the mvp-xml.sf.net).
I was using my old hack - custom XmlReader that emulates dummy DOCTYPE to enforce .NET's System.Xml (both XmlDocument and XPathDocument) to use ID info collected from a schema. But you know, as it turned out, that hack is quite limited - System.Xml is only recognizing ID attributes (not elements) and only for globally defined elements! Oh. Looks like that piece of code in System.Xml was designed only for DTDs, where all elements are globally defined and it works for schemas too only due to the unified implementation in System.Xml.Schema. Ok, so XPointer.NET's support for schema-determined IDs is going to be rather limited - only ID typed attributes and only for gloablly defined elements.
Leave a comment