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From "Kees Broenink" <kees.broen...@backbase.com>
Subject RE: Architectural concerns
Date Wed, 10 Aug 2005 10:56:07 GMT
Hi Torsten,

Thanks for your reply.

> And what about the root tag?
> You want to keep the pipeline well-formed.

Well Cocoon does not garantuee this. It is a common mistake (did it
myself quite often) to forget in a XSLT stylesheet to always set a root
tag (<template match="/"><myroot>...).

> Cocoon is *streaming* the XML through the pipelines.
> That's what you would expect from a today's XML pipeline
> architecture ...which is also the reason why you cannot
> react on XML values inside the stream from the sitemap
> level without buffering the whole process.

I was thinking out-of-the-box about functional/conceptual requirements.
Your reply is about technical implemention/performance issues. Of course
these are sometimes hard to separate because you cannot build something
which is impossible (my computer still makes no breakfast). But really,
if you take a step back it is hard to explain to new XML pipeline users
why they can select on a request parameter but not on a XML field.

Regards,
Kees


-----Oorspronkelijk bericht-----
Van: Torsten Curdt [mailto:tcurdt@apache.org] 
Verzonden: Wednesday, August 10, 2005 12:36 PM
Aan: dev@cocoon.apache.org
Onderwerp: Re: Architectural concerns



> Now to me the first generator is already a farce. I made an SQL 
> transformer that simply accepts the query as parameter in stead of
> using
> the XML stream.

I always thought it would be better to have a sql
query being executed *before* the transformation starts.
So from that point of view this does makes sense.

Altough... having sql statements inside the sitemap! *shiver*

> So this means we should allow:
> - not to have a generator at all (yes I thought about the
> consequences)

?

<snip/>

> - generator: starts a new stream (thus ignoring previous stream if
> present)
> - transformer: changes a stream (which could be empty at the  
> beginning)
> - serializer: ends the stream

And what about the root tag?
You want to keep the pipeline well-formed.

Sorry, not excited here.

> Related to this issue is the Cocoon Aggregate statement

Have a look into the cinclude transformer

<snip/>

> 2. selectors are evaluated before the pipeline is executed
>
> This basically means you can select on global, request and session
> fields because these are already set. But of course you also want to
> react on XML values in the stream. That is what you expect from an XML
> pipeline architecture.

Cocoon is *streaming* the XML through the pipelines.
That's what you would expect from a today's XML pipeline
architecture ...which is also the reason why you cannot
react on XML values inside the stream from the sitemap
level without buffering the whole process.

> In short: I want to be able to choose different transformers depending
> on the elements/attributes placed in the stream by the previous
> transformer.

Maybe you want to have a look into cocoon 1 :-P

cheers
--
Torsten


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