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From Stefano Mazzocchi <stef...@apache.org>
Subject Re: [SUMMARY] Viva la Multiplexer! (was: [Contribution] Pipe-aware selection)
Date Tue, 09 Apr 2002 16:59:13 GMT
Daniel Fagerstrom wrote:
> I believe that it is a better SoC to let the
> sitemap handle control structure and data flow and let the transformers
> transform single documents.

Absolutely agreed.
 
> > Furthermore, is there REALLY a difference between these two pipelines:
> >
> >                    - pipeline1 -
> >                   /              \
> >  request -> A -> X - pipeline2 - X -> C -> response
> >                   \              /
> >                    - pipelineN -
> >
> >
> >  request -> A -> P1 -> P2 -> P3 -> C -> response
> >
> > (where Pn are a group of Transformations/Actions etc.)
> >
> > Apart from how you would arrange them differently in the Sitemap, what is
> > the real need to have parallel processes?
> I assume that the above example uses a "multiplexer" that can choose sub
> streams from the input stream. You can achieve the same functionality with
> booth methods, but in the second example P1, P2 and P3 must "know" about
> each other. Consider an input document like:
> 
> <input>
>   <a> ... </a>
>   <b> ... </b>
>   <c> ... </c>
> </input>
> 
> with the multiplexer you can write general "a"-handling, "b"-handling and so
> on, sub pipelines  that can be reused in other contexts. For the second
> construction, the transformer P1 must know about the root node "input" and
> that "b" and "c" are supposed to be copied to the output, and similarly for
> P2 and P3.
> 
> To summarize: booth pipe-aware selection and multiplexers can be implemented
> in terms of xslt, but it distributes the control structure to booth the
> sitemap and the stylesheets, and it implies that the stylesheets must know
> about their contexts, which makes them harder to reuse.

I agree.

Keep in mind that SoC works only if the contract between concern islands
is solid.

If I were to bet on the solidity of something, XSLT would not exactly be
my first item in the list.

-- 
Stefano Mazzocchi      One must still have chaos in oneself to be
                          able to give birth to a dancing star.
<stefano@apache.org>                             Friedrich Nietzsche
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