• To: "'Jeni Tennison'" <jeni@j...>,"'Uche Ogbuji'" <uche.ogbuji@f...>
• Subject: RE: XPath 2.0 - how much of XQuery should it include?
• From: "Michael Kay" <michael.h.kay@n...>
• Date: Fri, 10 May 2002 15:36:59 +0100
• Cc: "'Jonathan Robie'" <jonathan.robie@d...>,<xml-dev@l...>
• Importance: Normal
• In-reply-to: <581557137064.20020510102325@j...>
• Reply-to: <michael.h.kay@n...>

> "Shortcutting" means that you only evaluate the first part of 
> the expression if you can determine the result of the 
> expression, correct? In XPath 1.0, 'and' and 'or' are shortcutting:
> 
> 
> I hadn't noticed that this changes in XPath 2.0 (it's not 
> listed as one of the incompatibilities):
> 

Yes - this should have been listed as an incompatibility.

This change was made because database systems need to use indexes to
evaluate boolean expressions. In a database system, if someone writes

   colour=my-favourite-colour() and home-town="Wigan"

then if you have an index on home-town, you want to use it.

I've been thinking we might try to add something to XSLT that imposes
rules for XPath-in-XSLT that are stricter than the rules in XPath itself
to deal with such situations.

Michael Kay

• Follow-Ups:
  • Re: XPath 2.0 - how much of XQuery should it include?
    • From: "Rick Jelliffe" <ricko@a...>

• References:
  • Re: XPath 2.0 - how much of XQuery should it include?
    • From: Jeni Tennison <jeni@j...>

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