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Re: Selector and Field XPaths (for Schema 1.1)

From: Henry S. Thompson <ht@cogsci.ed.ac.uk>
Date: 20 Nov 2002 14:27:23 +0000
To: Stefan Wachter <Stefan.Wachter@gmx.de>
Cc: xmlschema-dev@w3.org
Message-ID: <f5bsmxwe2pg.fsf@erasmus.inf.ed.ac.uk>

Stefan Wachter <Stefan.Wachter@gmx.de> writes:

> 1.
> 
> The spec. defines BNFs for the valid XPaths. However, it also states
> (at 2.2) that XPaths whose abbreviated forms correspond to the BNFs
> are also valid with the restriction that only the 'child' (and
> 'attribute' axes in case of fields) are used.
> 
> Yet, the BNFs also use the 'self' and the 'descendant-or-self' axes.
> Therefore I think that these axes should also be allowed for the
> XPaths covered by (2.2).

'self' is '.', which is allowed by the BNF, as is '//', which is
descendant-or-self.

> 2.
> 
> The BNFs allow the '//', i.e. a 'descendant-or-self' step only at the
> beginning. I think this restriction is not necessary because it does not ease
> implementations and is conceptually not justified.

The restriction to one, initial, use of //, is intended to reduce
implementation complexity for streaming implementations.

> 3. The 'descendant' axis should also be allowed.

What use case do you have in mind?

ht
-- 
  Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh
          W3C Fellow 1999--2002, part-time member of W3C Team
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	    Fax: (44) 131 650-4587, e-mail: ht@cogsci.ed.ac.uk
		     URL: http://www.ltg.ed.ac.uk/~ht/
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Received on Wednesday, 20 November 2002 09:27:26 GMT

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