Re: XPath that returns nothing

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Subject: Re: XPath that returns nothing
From: Michael Kay <mike@xxxxxxxxxxxx>
Date: Wed, 28 Sep 2011 10:56:55 +0100

incidentally () is the _only_ expression that is guaranteed to return nothing and to be safe in a schema aware xslt2 processor. Other expressions that may statically be determined empty may raise an error.

No, that's not quite true in XQuery and even less true in XSLT. XSLT doesn't do pessimistic static type checking. Even in XQuery, you're not allowed to raise a static error for something like

*[current-date() lt xs:date('1900-01-01')]

(which is 'guaranteed to return nothing' but cannot, strictly speaking, 'statically be determined empty')

Michael Kay
Saxonica

Current Thread

Re: XPath that returns nothing, (continued)
- Andrew Welch - 27 Sep 2011 08:43:00 -0000
  - Vasu Chakkera - 28 Sep 2011 05:35:46 -0000
  - David Carlisle - 28 Sep 2011 09:01:54 -0000
    - Michael Kay - 28 Sep 2011 09:57:08 -0000 <=
    - David Carlisle - 28 Sep 2011 10:10:44 -0000
    - Andrew Welch - 28 Sep 2011 10:11:22 -0000
    - David Carlisle - 28 Sep 2011 10:14:13 -0000
    - Andrew Welch - 28 Sep 2011 10:18:23 -0000

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