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Re: Poorly researched observations on <xsd:key>, <xsd:keyref> and <xsd:unique>

From: Henry S. Thompson <ht@cogsci.ed.ac.uk>
Date: 12 Feb 2001 10:12:01 +0000
To: "Arnold, Curt" <Curt.Arnold@hyprotech.com>
Cc: "'www-xml-schema-comments@w3.org'" <www-xml-schema-comments@w3.org>
Message-ID: <f5bvgqgxlam.fsf@cogsci.ed.ac.uk>
"Arnold, Curt" <Curt.Arnold@hyprotech.com> writes:

> {selector} specifies an XPath expression [XPath] relative to
> instances of the element being declared. This must identify a node
> set of subelements (i.e. elements contained within the declared
> element) to which the constraint applies.  Whether an arbitrary
> XPath expression (for example, one that uses the id() function or
> the parent axis) identifies a node set of subelements of the context
> element can't be determined until applied to the document being
> validated.  It would be better to constrain selector so that only
> expressions that always return subelements are allowed, such as
> saying that the xpath attribute must be a UnionExpr where any
> AxisSpecifier is restricted to the set (child, descendant, self or
> descendant-or-self, //, .).

We've done essentially this for the next WD.

  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@cogsci.ed.ac.uk
		     URL: http://www.ltg.ed.ac.uk/~ht/
Received on Monday, 12 February 2001 05:12:11 UTC

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