Saturday, July 7, 2007

XML Schema composition problems

I dived into the mysteries of XML Schema composition and found several things that are not so clear to me with the semantics of chains of xsd:include and xsd:inport, with referencing names across schema documents and things related to both.

See the thread that I started at xmlschema-dev mailing list:

I also saw a bug report related to some of my concerns reported as [Bug 4838] Chameleon behavior

I did not get a clear understanding of the issues that I raised.

I do understand that:

  • circular dependencies is OK
I still don't know the correct expected behavior in the case where there's a chain of xsd:include and xsd:import: does xsd:inclue should allow names from namespaces other than the one in the including document? If so, in which cases?

I also still do not understand the semantics of referencing names beyond the bounds of the same schema document as far as schema composition is involved. Should xsd:any and ref consider only names defined in the same schema document and in schema documents that are imported and included in it? Or perhaps should xsd:any and ref consider only names in the same schema document and in schema documents that import or include the schema document that they appear in? Or perhaps both? What exactly are the rules? I cannot make them out from the standard.

Not that it helps me, but it is still interesting to see the list of reported bugs to XML Schema when you look for "schema composition" in the bug tracking system:

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