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Bob wrote:
>XPath says that nodes should be returned in 'document order', which
>becomes a non-trivial in the case of some expressions involving
>the union operator. One developer has a solution, but it is of
>O(tree-size) complexity. Do that against a 30mb document, and
>suddenly XPath isn't nearly as attractive.
Hi Bob,
If 'document-order' is required,
$foo/bar | $cheese/melty
certainly means more work. To the best of my knowledge, Xalan2
for Java seems to follow this 'requirement' even for expressions
involving the union operator. In the case of '$foo/bar | $cheese/melty'
does the order of the returned node-set matters to the user? I can
understand if a predicate is used (example from the spec):
preceding::foo[1] != (preceding::foo)[1]
---------------------------------
Evan wrote:
>Actually, XPath nowhere says that nodes must be returned in
> document order. Node-sets are sets; they have no order.
Although, it is not stated explicitly that nodes must be returned in
document order, if a predicate is used in a location step, the
ordering becomes relevant. You know, it would be more helpful if this
issue is described under section 3.3 Node-sets.
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Ramin wrote:
> '//' just about made me want to hurl
> every time I thought about how much work it generated under the hood.
> Then I would remember how useful it was to end-users and calm down (:-)
It is convenient and it invites abuse. I have had a brief
moment with XPath through XSLT. I often wondered
how other users take advantage of XPath's expressiveness
esp. with other axes such as 'ancestor', 'preceding' or 'following'.
---------------------------------
Mike Kay wrote:
> ... <xsl:if test="//a=//b">
This is a nasty XPath expression. It is a valid expression but all
too convenient for the user. The developers have no choice but to tackle
it head on while the users will be delighted (esp. lazy power users).
---------------------------------
I didn't expect such a huge response to the subject, else, I would have
replied earlier. xml-dev rocks!
Kelvin
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