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Consider 3 schema documents A, B, and C for the same target namespace. B includes A; C wants to redefine B by modifying a component define in A. Is this possible? <redefine schemaLocation="B"> <simpleType name="aTypeDefinedInA"> In section 4.2.2 of the structure spec, "In all cases there must be a top-level definition item of the appropriate name and kind in the <redefine>d schema document." Note that it says "redefined schema document", which implies that the above redefinition is invalid. Then how would one write such a C? <include schemaLocation="B"/> <redefine schemaLocation="A"> <simpleType name="aTypeDefinedInA"> will probably give "duplicate component" for aTypeDefinedInA, because you get it both from B and from the redefinition. Possible solutions: - No way to define such a C - Make the second approach (include+redefine) work: it doesn't have duplicate components - Make the first approach work: redefine schemas as opposed to redefine schema documents. That is, loose the cited constraints.
On its telcon today, the Working Group discussed this and other issues related to schema composition and concluded (not without some pangs of regret) that for scheduling reasons it is not feasible for us to resolve them before we go to Last Call. The WG continues to believe that this issue is important and should be resolved; our decision to close the issue for now reflects the fact that we have not been able to reach consensus on how to resolve the problems related to composition, coupled with the observation that for the most part, users are able to avoid the problems by avoiding problematic constructs in their schema documents. The cost of delaying XSDL 1.1 for these issues is thus high, while the practical benefit for users is not as high as it might be. The Working Group continues to hope that this issue can be resolved at some point in the future. Accordingly I am closing this issue with a disposition of LATER.
A wording proposal intended to resolve this issue in part is at http://www.w3.org/XML/Group/2004/06/xmlschema-1/structures.b2224.html (memger-only link). The resolution is only partial, because the proposal does not actually repair any problems directly; it only deprecates xs:redefine in order to warn schema authors away from it and make it possible to remove the feature at some future date.