Re: [xsl] Unexpected Context Node at Points in XPath Expression

Subject: Re: [xsl] Unexpected Context Node at Points in XPath Expression
From: Abel Braaksma <>
Date: Wed, 05 Sep 2007 01:07:57 +0200
I find it very worrying that either of your expressions select anything. I tried the page you mentioned and tried to visually follow your path, but couldn't find any match. Then I thought that maybe the tool was smarter than I, so I downloaded/installed it. Tried your queries again: nothing.

Next I cut n pasted the source HTML so I could process it normally without the fuzz and noise of other tools (not knowing what they do, where they rely on, etc). I quickly found that:

1. There is no <h2> element anywhere that document
2. There is a <h3> element, but that does not have any siblings of type <ul>
3. In the expression you don't select <ul>, but any elements
4. I tried to understand your English description of what you are trying to achieve, but there are no <ul> elements that are siblings to <h3>

But you say "following". So maybe I misunderstood. In your code you use following-sibling with some counting back and forth. Not along the following::* axis (there are much deeper nested <ul> elements).

Your question was about the difference in your XPaths. You use the id() function (note that it only works when there is actually a DOCTYPE present that declares an attribute as type ID; often this is not the case, so in practice I don't see id() used that often), which selects all elements (like the DOM getElementsById()) with the selected ID. This means that in your second expression you are basically searching from the root (bodyContent) on each step. In your first, you are using the child axis to start from.

Because I can't see a document that possibly matches your XPath expression, I can't see where it goes wrong.

Sorry I couldn't be of any more help.

-- Abel Braaksma

Michael Terry wrote:
Unexpected to me, at least.

I've been familiarizing myself with XPath for a project by browsing
around the Internet with the Firefox extension XPath Checker.

On this page:

... I tried the following:

- count(preceding-sibling::*)]

... which I expected to select the 7 ul elements following the
specified h2. The next query DOES do that:

- count(id('bodyContent')/h2[1]/preceding-sibling::*)]

The stuff I had to add in I had expected was already present as the
context node. Why was I wrong?

- mt

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