RE: How to transform flat structure into hierarchical one?

[Jeni Tennison <Jeni.Tennison@xxxxxxxxxxxxxxxx>]

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@xxxxxxxxxxxxxxxx



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