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Re: missing XPath axis

• From: David Carlisle <davidc@nag.co.uk>
• To: "xml-dev@lists.xml.org" <xml-dev@lists.xml.org>
• Date: Sat, 24 Sep 2011 18:07:23 +0100

On 24/09/2011 16:56, John Cowan wrote:
> Another point is that an axis has to have unambiguous ordering (okay,
> there's the namespace axis, but who cares about that?)  It is not
> clear where the self should go on a child-or-self axis: first, last,
> in the middle?

well actually it would have to go first (as it would be a forward axis 
so return nodes in document order), but mainly I suspect it's not 
provided as it's hard to find a natural use case for it and it's longer 
to type that .|node() which would be the equivalent (if used as the 
first step (or in any step in xpath 2).

ancestor-or-self:: is used often for finding the nearest in-scope 
attribute value (for lang or id of nearest containing section, etc.)

descendant-or-self:: is, as Ken just commented, used for defining // 
(although actually that was probably a mistake, it was done that way 
intentionally so //p[1] meant the first p in each section, whereas most 
people probably expect // to be defined as descendant:: and have //p[1] 
mean the first p in the document, but that's all water under the bridge 
now:-)


David

• References:
  • missing XPath axis
    • From: "Johannes.Lichtenberger" <Johannes.Lichtenberger@uni-konstanz.de>
  • Re: missing XPath axis
    • From: John Cowan <cowan@mercury.ccil.org>