Let me give a bit of background to the use case motivating the question.

I want to find all reviews written by people that only wrote 1 review. I
wrote

collection($sp:reviewsColl)/descendant::reviews[not(review[2])]

but reviews has a @person attribute and that person may have 1 or more
reviews in another collection - so that doesn't work.

The thing  that seemed most natural to fix this was to supplement the
predicate to say there should be no sibling review by the same
reviews/@person.





On Sun, Jan 5, 2014 at 8:54 PM, Michael Kay <[email protected]> wrote:

>
> On 5 Jan 2014, at 16:50, Ihe Onwuka <[email protected]> wrote:
>
> > If x is the document element of a document in a collection, is it the
> sibling of y that is the document element of another document in the same
> collection?
>
> No.
> >
> > If not why not?
>
> "Why" questions are very difficult to answer. Do you want a historically
> accurate answer (was the question debated at a WG meeting, who argued which
> position, how did the vote go, and why did individual members vote as they
> did?) - because it's very rarely possible to give one. Or do you want a
> post-hoc justification (can you think of a sensible reason that anyone
> might have designed it this way?)
>
> One post-hoc justification is that collections are unordered, whereas axes
> are always ordered.
>
> Another is that documents may belong to more than one collection.
>
> Michael Kay
> Saxonica
>
>
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