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[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: which xml schema tools do it right concerning including at
 Hi Dare, > However we don't think that on the one hand an imported schema that > redefines the XML namespace can be ignored when validating the > schema but then on the other hand should override the meaning of the > contents of the XML namespace when using the schema to validate an > instance document. This is rather inconsistent and where I come from > we call that "Crazy Talk"... I'm not sure that I follow this (things get rather confusing when you're talking about validating schemas with the SforS, so we might be talking at cross purposes). When you validate a schema against the SforS, the SforS is the schema and the schema is the instance. The only imported schemas that are relevant when validating a schema document against the SforS are those schemas that are imported into the SforS. The SforS includes an xs:import for the XML namespace; this imports the definitions in the schema at http://www.w3.org/2001/xml.xsd. Any xs:import elements in the schema that you're validating have no effect on the SforS -- they're just treated as elements like any other. So if when you talk about "validating the schema" above, you mean carrying out an XML Schema validation of the schema document using the SforS, then it's true that imported schemas (referenced through xs:import in the schema document), whatever their namespace, can be ignored. At this level, you're checking the XML representation of the schema, nothing more. When you actually validate an instance against the schema, though, the schema is turned into an abstract schema information set by parsing the XML representation and resolving the imports, includes and redefines. The only imports, includes and redefines that are used to construct the schema information set are those that are referenced by the schema (and by the things it references, recursively). A validator might ignore certain schema documents if they are imported/included/redefined twice, but otherwise has to resolve them in order to construct the schema. So if when you talk about "validating the schema" above, you mean carrying out this validation of the semantics of the schema document and its imports/includes/redefines and the construction of a schema information set, then yes, of course imported schemas cannot be ignored (unless they have already been imported). As far as I can see, XML Schema does not provide any special status for the XML namespace. So in a way talking about "overriding the meaning of the XML namespace" doesn't make much sense because as far as a schema validator is concerned, there's nothing to override. The meaning that you provide for that namespace through your imported schemas is really up to you, in just the same way as you can define XHTML or XLink or any other "standard" markup language with whatever schema you like. It's not particular wise, but there's nothing within XML Schema that gives validators special knowledge of any namespaces other than the XML Schema namespaces. > If one wants to alter the meaning of the contents of the XML > namespace then <xs:redefine> can be used to achieve that. Yes -- you could redefine the schema for the XML namespace at http://www.w3.org/2001/xml.xsd, and then import that into your schema. (But remember that you can only redefine schemas that have the same target namespace as the schema that you're defining, so you can't use a redefine instead of an import, only *as well*.) Cheers, Jeni --- Jeni Tennison http://www.jenitennison.com/ 
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