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Re: Does the count() function require access to the wh

Subject: Re: Does the count() function require access to the whole subtree?
From: Dimitre Novatchev <dnovatchev@xxxxxxxxx>
Date: Sun, 12 Jan 2014 13:35:14 -0800
Re:  Does the count() function require access to the wh
On Sun, Jan 12, 2014 at 11:27 AM, Michael Kay <mike@xxxxxxxxxxxx> wrote:
> If you are evaluating count() or exists() on a sequence of nodes S, then when you encounter
> a node N that is a member of this sequence you know its impact on the result as soon
> as you see its start tag; you do not need to look at its subtree

Typically, the nodes are part of the streamed document -- not items in
a sequence.
Let's say, we want to find the count of all children element (of the
context node) named "x".

Even if it is guaranteed that any "x" doesn't have descendants named
"x", in order to find the (k+1)st
occurrence of an "x" element from the k-th occurrence, we must
traverse the complete subtree of the k-th occurrence of "x",
and the subtrees of any intervening non-"x" siblings.

If this is called "inspection" -- then this inspection traverses
nearly the whole document. Even it doesn't "consume" it (I don't know
what "consume" exactly means), then, because the document has been
traversed during this "inspection", then the traversed part is no
longer "consume"able or even "inspect"able.

Anyway, we need someone to explain this situation.

Dimitre Novatchev
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