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From Miles Elam <>
Subject Re: map:aggregate / map:part does only work with XML files?
Date Mon, 01 Sep 2003 18:12:39 GMT
rufio wrote:

>on Mon, 1 Sep 2003 17:43:14 +0200 Bertrand Delacretaz
><> wrote:
>>I think the current way of doing aggregation makes perfect sense if
>>you think of aggregating pipelines, not only generators.
>>AFAIK there are no plans to change this.
>And I thing aggregator should be able to take anything that produces
>SAX events - generators/resources/whatever, so people didn't have to use
>pipeline-for-generator workaround.

It can.  <map:part src="..."/> can take a remote URI, a local absolute 
URI, a local relative URI, and the output of another pipeline.  What 
exactly is the limitation?  For all intents and purposes from the user 
point of view, <map:part/> is a generator.  If readers et al. (read: 
possible non-XML content) were allowed into <map:aggregate/>, Cocoon's 
XML processing contracts would be horribly broken.  In addition, putting 
what amounts to a full pipeline in the aggregator has issues as well 
which I will explain below.

Having these resources in another pipeline has the added advantage of 
debugging.  If it were specified in the aggregator, it would be much 
harder to isolate any problems.  As a separate pipeline URI, unit tests 
(with finer-grained units) become simpler and more powerful.  You can 
test the aggregated results and the standalone results independently.  
Having worked with Cocoon's sitemap for a while now, I cannot stress 
enough how often this comes up.

When finished testing, the standalone URI can be made a private, 
internal-use only URI.  If you find that your sitemap is becoming 
unmaintainable because of these extra matchers etc., have you considered 
reviewing your sitemap to make sure your URI space is clean (eg. reduce 
or eliminate redundant matchers)?  Also, with subsitemaps, it possible 
to split up a large and unweildy sitemap into smaller, logical 
subsitemaps for readability.

So what were the use cases for needing these added semantics to the 
aggregator that outweigh what was just mentioned?

- Miles Elam

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