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Re: sub-tree filtering proposals
On Tue, Jun 08, 2004 at 12:36:23PM +0200, Frank Strau? wrote:
> >
> > //interface[type="ethernet"][connector="present"]
>
> This kind of operation first builds the set of all <interface>s which is
> then limited to those with type="ethernet" and this subset is then limited
> to those with connector="present". This means a sequence of predicates is
> not commutative, in contrast to the logical AND operator. An example where
> this would be signifcant is this:
> //interface[type="ethernet"][position()=last()] would address the last
> ethernet interface, while
> //interface[position()=last()][type="ethernet"] would address the last
> interface, if it is an ethernet interface, otherwise an empty node set.
>
> Xpath predicates (the parts in brackets) may contain boolean operators
> ("expr1 and expr2","expr1 or expr2", "not(expr)").
True in general.
However, the proposed required minimal subset does not include things
like last() or position() - only simple comparisons of element/attribute
values (no other operators). Do you think the fact that sequences of
predicates are not commutative is still important in this special
restricted case?
/js
--
Juergen Schoenwaelder International University Bremen
<http://www.eecs.iu-bremen.de/> P.O. Box 750 561, 28725 Bremen, Germany
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