[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: Substitution Groups
"Paul Spencer" <xml-dev@b...> writes: > I have been trying to work with a set of published schemas that use > substitution groups and found that the schemas themselves were not valid. So > I started looking at other published schemas that use them and found that > these were also not accepted by one or more XML processors (I tried Xerces, > MSXML and .NET) or used some very complex work-arounds. I'd be very interested to see concrete example docs and error messages -- this has not surfaced before as an interop problem. > Are substitution groups practical when the head of the group is in a > different schema document from the members of the group? Yes. > The scenario is this: > File A defines a complex data type AType and an element A of that type. > > File B defines a complex type BType that is an extension of AType and an > element B of that type. Element B is in the substitution group for element > A. Yup, good design pattern. > It as an error if File B does not <include> file A since the XML Processor > can't find the head of the substitution group. File B must <import> file A's namespace. That's the minimum necessary to declare victory. > File A must <include> file B otherwise an instance that uses element B will > be invalid. No, bad idea. Instance documents and/or validators and or validation API users must find/point to both schema documents. There are a number of ways to do this -- which ones work/are sufficient is - you may well point to file A in the <import> in file B; - your instance doc is likely to point to file A and/or file B; - your invocation might do likewise; - your validator may do it all on the basis of the namespace URIs in your instance. ht -- Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh Half-time member of W3C Team 2 Buccleuch Place, Edinburgh EH8 9LW, SCOTLAND -- (44) 131 650-4440 Fax: (44) 131 650-4587, e-mail: ht@i... URL: http://www.ltg.ed.ac.uk/~ht/ [mail really from me _always_ has this .sig -- mail without it is forged spam]
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