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RE: How to transform flat structure into hierarchical one?
- To: "Paulo Gaspar" <paulo dot gaspar at krankikom dot de>
- Subject: RE: How to transform flat structure into hierarchical one?
- From: Jeni Tennison <Jeni dot Tennison at epistemics dot co dot uk>
- Date: Thu, 08 Jun 2000 10:14:54 +0100
- Cc: <xsl-list at mulberrytech dot com>
- References: <3.0.6.32.20000607172722.0116d990@NTServer>
- Reply-To: xsl-list at mulberrytech dot com
Paulo,
>Aleksandrs has performance concerns. Getting the data already sorted
>from the database and having the XSL relying on that ("team work")
>is, probably, the most performing solution.
I absolutely. It's just that...
>Still, I am learning a LOT from your answers!
...that's the primary aim of my contributions ;)
>I am not asking you to lecture me on "Muenchian techniques". (This
>list already takes a lot of your time as it is.) What I am asking is
>for some pointers: URL's, book names and/or other locations of
>interesting content about that subject.
>
>(In the end it is in M. Kay's book I am talking about all the time...
>...but I did not read the whole thing just yet.)
The Muenchian technique is a grouping method discovered by Steve Muench,
and explained on this list by the man himself:
http://www.mulberrytech.com/xsl/xsl-list/archive/msg12260.html
Using keys, Steve increased the efficiency of grouping when compared to the
old technique of using the preceding-sibling or following-sibling axes and
predicates.
Unfortunately, Steve discovered this *after* Mike Kay's book came out. I
have added a special note to my copy at the bottom of page 560 to help
remind me to use the Muenchian technique instead whenever I have a grouping
problem to solve.
In addition, there was some discussion a few weeks ago about the best way
of comparing nodes when using this technique. The two options use either
generate-id() or counting the number of nodes in a node set union. These
were elucidated by the XPath guru, David Carlisle, as archived at:
http://www.mulberrytech.com/xsl/xsl-list/archive/msg13065.html
I believe that it's still up in the air about which is most efficient -
this is probably processor dependent.
Finally, if you want to learn more about keys, I learnt a lot from the
online illustration from Crane Softwrights Ltd. at:
http://www.cranesoftwrights.com/resources/xslkeys/index.htm
I hope these pointers are useful to you.
Cheers,
Jeni
Dr Jeni Tennison
Epistemics Ltd, Strelley Hall, Nottingham, NG8 6PE
Telephone 0115 9061301 • Fax 0115 9061304 • Email
jeni.tennison@epistemics.co.uk
XSL-List info and archive: http://www.mulberrytech.com/xsl/xsl-list