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Re: implementing redefinitions

From: Henry S. Thompson <ht@inf.ed.ac.uk>
Date: Wed, 17 Aug 2005 16:00:04 +0100
To: "Michael Kay" <mike@saxonica.com>
Cc: "'Kasimier Buchcik'" <kbuchcik@4commerce.de>, "'XML-SCHEMA'" <xmlschema-dev@w3.org>, www-xml-schema-comments@w3.org
Message-ID: <f5boe7wd2x7.fsf@erasmus.inf.ed.ac.uk>

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Thanks for this clear and succinct statement of the situation, which I
think the XML Schema WG should take into consideration as it tries to
clarify the whole schema composition story for XML Schema 1.1.

Michael Kay writes:

> In QT we have to consider a query or transformation as a whole. Documents
> are annotated with types, and we need to have confidence that when we see a
> type annotation, we know what type it refers to. The processing model
> assumes that types can be identified by a QName. For this to work, we can't
> have two different types with the same QName within the scope of a query or
> transformation (in the XQuery case, this scope is an entire database...).
>
> This is something of a pain, because it means you can't use XSLT to
> transform from one version of a schema to another version of the same schema
> if it uses the same namespace. Clearly we need a versioning story, as you
> have often said yourself...
>
> But it also affects redefine. If I load two documents as inputs to a query
> or transformation, one validated using schema A, and the other using schema
> R which redefines schema A, then I've got two types with the same name, and
> everything (in particular, QT type checking) breaks.

What do you (Mike) think _should_ happen in this case?  Whose
responsibility is it to detect this condition, and what should they do
when they do?

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@inf.ed.ac.uk
                   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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Received on Wednesday, 17 August 2005 15:00:16 GMT

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