Re: [xsl] Pattern: Processing Unwrapped Repeating Groups

[Wendell Piez <wapiez at mulberrytech dot com>]

Hi Eliot,

At 09:49 AM 1/30/02, you wrote:
>In trying to solve a problem in the style sheet I'm currently developing
>I stumbled on a pattern that I hadn't seen anywhere in my reading on XSL
>processing--it's probably obvious to most but it took me a while to
>figure it out so I thought I would share it.
>
>The input data consists of what I call "unwrapped repeating groups, that
>is, a content model like this: ...

It is a known pattern, but it's not actually obvious to most. (For example, 
I just reviewed an otherwise-excellent XSLT how-to book that recommends -- 
ouch! -- a disable-output-escaping-based solution to this problem.) For the 
most part, we've seen this technique subsumed under grouping, which 
(largely to the work of Jeni T.) is a fairly-well understood problem area. 
(Check out her site, http://www.jenitennison.com.)

But it's broader than what most people think of as grouping, and really 
ought to be distinguished for itself. And you're right, I haven't seen it 
covered as such in the literature. (Watch out or someone will name it after 
you.)

When element types aren't enough to distinguish how the groups should be 
made -- one example is introducing hierarchy into a flat structure where 
"nested" sections are distinguished only by h1, h2, h3 elements and so 
forth -- sometimes we use keys to select elements that go with the 
"starter" element of each group.

The only slight improvement I'd suggest to your approach is to use the 
'following-sibling' axis instead of 'following'. You'll find it much more 
efficient over large data sets, since 'following' is going to go further -- 
sometimes much further -- than just children of the same parent.

Cheers,
Wendell


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Wendell Piez                            mailto:wapiez@mulberrytech.com
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