[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: XML Schemas and extension
Jeff Rafter <jeffrafter@e...> writes: > I know that we seemed to finish the "ref'ing vs. inlining" discussion and > all seemed pretty satisfied, but I was wondering how all of this fits into > type derivation when using extension. > > I know that, > > "A complex type which extends another does so by having additional content > model particles at the end of the other definition's content model, or by > having additional attribute declarations, or both. > > NOTE: This specification allows only appending, and not other kinds of > extensions. This decision simplifies application processing required to cast > instances from derived to base type. Future versions may allow more kinds of > extension, requiring more complex transformations to effect casting. " > > I have read through the spec. and can't seem to come up with an answer to > the following, unless it fits into the above cited "future revision" caveat > : Can an element in be redeclared in a derived (by extension) complexType? > > <complexType name="Foo"> > <element name="bar" type="int"> > </complexType> > > <complexType name="Foo2" base="Foo" derivedBy="extension"> > <element name="bar" type="int"> > <element name="bar2" type="int"> > </complexType> > > I apologize if there is an obvious answer in the specification that I am > missing or not comprehending. Derivation by extension can be understood as syntactic sugar. It's the effective type definition that has to satisfy the constraints on types such as no-duplicate-elt-name-with-different-types. So consider the effective type definition: <complexType name="Foo2"> <sequence> <element name="bar" type="int"> <element name="bar" type="int"> <element name="bar2" type="int"> </sequence> </complexType> Nothing wrong with that, so the derivation is OK. ht -- Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh W3C Fellow 1999--2001, part-time member of W3C Team 2 Buccleuch Place, Edinburgh EH8 9LW, SCOTLAND -- (44) 131 650-4440 Fax: (44) 131 650-4587, e-mail: ht@c... URL: http://www.ltg.ed.ac.uk/~ht/
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