Re: [xsl] how to rearrange nodes based on a dependency graph?

[Wendell Piez <wapiez@xxxxxxxxxxxxxxxx>]

Guenther,

I didn't follow the start of this thread closely, so I can't give a 
particular solution, but...

At 05:52 PM 12/20/01, you wrote:
> I still can't see what this would do. This isn't about simply
> filtering out nodes with dependencies, it is filtering out
> those nodes that had already been processed because of the
> dependency graph walk. The only way I can see to do this is
> to somewhere keep a list of the processed nodes, but how
> can I do that with XSL? (I guess I can't).

Right: such an approach would not be The XSL Way. XSLT processing is 
designed to be as side-effect free as possible; and unfortunately relying 
on the order nodes happen to be processed in a given implementation (or 
even relying on the assumption that they will be processed in any order at 
all) is considered to be relying on a side effect.

>  The only alternative
> would be to decide for every node if it would have been in
> the dependency graph of any prior node. But that would mean
> that all dependency graphs need to be always chased for every
> node, that's kind of mind-boggling.

It is, which is why people are trying to apply keys to approach the 
problem: keys are the usual XSLT device for creating associations between 
elements based on relationships other than the structures they come in (in 
your case, cross-references between the elements). The fact that a given 
key value can return several matching nodes is an important feature, 
allowing for grouping (which idiom has made Steve Muench immortal) -- which 
may be exactly what you really need -- and other kinds of operations that 
defy the logic of document order.

I think a key approach would do it for you; if even that comes up short, 
the next strategy to consider would be to break your processing into two 
passes. XSLT gets really powerful when you use a stylesheet to generate 
either a new source file optimized for the next pass, or a second 
stylesheet to run over the same source.

Does that suggest directions for you to think in?

Cheers,
Wendell


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Wendell Piez                            mailto:wapiez@xxxxxxxxxxxxxxxx
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