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- To: Paul Prescod <email@example.com>
- Subject: Re: [xml-dev] Subtyping in XML
- From: firstname.lastname@example.org (Henry S. Thompson)
- Date: 05 Sep 2002 16:32:55 +0100
- Cc: Jeff Lowery <email@example.com>, <firstname.lastname@example.org>
- In-reply-to: <Pine.LNX.4.30.0209050401410.4527-100000@latte.ActiveState.com>
- References: <Pine.LNX.4.30.0209050401410.4527-100000@latte.ActiveState.com>
- User-agent: Gnus/5.0808 (Gnus v5.8.8) XEmacs/21.2(beta13) (Demeter)
Paul Prescod <email@example.com> writes:
> On Wed, 4 Sep 2002, Jeff Lowery wrote:
> > What you're saying is that base members come before extended members? That's
> > fine, and it's not possible to extend (A, B, C) with (A, B, C, C*) in
> > XML Schema, although it is possible to extend it to (A, B, C, D, C*).
> > It's that last case that I consider Not So Bad, but Paul seems to find
> > objectionable.
> Base type: TRUE|FALSE
> Extended type: ((TRUE|FALSE), TRUE)
Sorry, just to be clear, those are DTD-notations for content models
with element names, nothing to do with simple types or booleans, right?
> This will defacto extend the enumeration and worse, allow two conflicting
> values at once.
Using the word enumeration here is potentially misleading -- it's
usually used in DTD/schema context to discuss enumerated values for
attributes/simply-typed elements. If that's how you're using it, the
above is _not_ possible in W3C XML Schema.
> Most SAX filters will not guard against these kinds of things.
The semantics you attribute to your element names etc. is surely your
business, and I wouldn't expect SAX or any other syntax-level tool to
Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh
W3C Fellow 1999--2002, part-time member of W3C Team
2 Buccleuch Place, Edinburgh EH8 9LW, SCOTLAND -- (44) 131 650-4440
Fax: (44) 131 650-4587, e-mail: firstname.lastname@example.org
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