Re: [xsl] Diagram of XPath axes
2012-05-24 17:07:14
Hi Mike,
In teaching, I have used precisely the same approach as Ken,
comprehensively dividing the document into the self, ancestor,
descendant, following and preceding axes, all in relation to "me".
It is also worth pointing out, however, that there is some potential
confusion, in that ancestors do appear "before me" in document order,
while descendants appear "after me" in document order, even though (as
Ken and others have noted), ancestors aren't yet done when I'm done, and
descendants are all done before I'm done.
The human brain being what it is (rather messy), we then mix up the
definition of document order with the specification of the different
axes, and there we are. Yet the concepts are clean, if we allow them to be.
So yes, the preceding axis reaches nodes that occur *entirely* before
me; and that necessarily excludes ancestors. By the same token, not all
nodes before me in document order will precede me -- at least as long as
I have an ancestor (which all nodes must, except document nodes).
Cheers,
Wendell
On 5/24/2012 8:58 AM, mlcook(_at_)Wabtec(_dot_)com wrote:
Ken Holman's diagram is the one I had seen before that summarized lots of info
concisely. I'm sure I've seen it on xsl-list or somewhere else, but don't
remember where.
Otherwise, Ihe Onwuka's suggestion does have tutorial information, but I didn't
see an overall diagram.
Scott Trenda pointed to a site with diagrams for individual axis access which
looks helpful.
Syd Bauman also points to tutorial diagrams for individual axes with examples,
and one final summarizing diagram.
One additional question, please:
Preceding nodes do not include ancestors, which I've thought is odd. It
includes siblings, but not parent or grand-parent, etc.
When looking at an XML file in an editor, ancestors surely seem to be preceding
where I am in the document.
But perhaps "preceding" means nodes before "me" but not including anything that contains
"me".
Is that a useful way to look at "preceding"?
Thanks again, Mike
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