• To: <xml-dev@l...>
• Subject: Re: status of "collections" in XPath / XQuery
• From: "Rick Jelliffe" <ricko@a...>
• Date: Wed, 30 Jan 2002 17:47:12 +1100
• References: <002701c1a8ee$3cb37040$78fe0250@pcukmka>

 From: "Michael Kay" <michael.h.kay@n...>
 
>   Is there thought going on regarding constraints on collections (when they
> are defined)?  I may want to have all
>   invoice numbers in a collection be unique.
> 
>   I haven't seen any proposals that address that. Certainly, XML Schema
> doesn't provide any cross-document validation.
 
The XLlinkIt validation language at www.xlinkit.com is aimed squarely at this
kind of problem, I think. (Christian Nentwich who sometimes posts on this list is, 
I believe, one of the programmers involved in it.)  

Schematron can do some kinds of inter-document validation, in particular
when there is a link in one document to another, e.g. to a controlled vocabulary.
But it lacks a for-each operator, and so is weak for collections. Xpath 2
may help in this, I don't know.

I gave up trying to figure out a Schematron expression to do this, but undoubtedly
something inefficient based on counting and the document() function could be
possible. 

Cheers
Rick Jelliffe

• References:
  • RE: status of "collections" in XPath / XQuery
    • From: "Michael Kay" <michael.h.kay@n...>

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