Re: [PROPOSAL] Pipeline Level Flow Extension

[Ovidiu Predescu]

Hi Michael,

On Monday, Oct 28, 2002, at 07:25 US/Pacific, Michael Melhem wrote:

Hello Cocooners,

I have a proposal for "pipeline level flowmaps" (and flowmap chaining)
as an extention to the existing sitemap-level flowmaps.

This proposal is based on the assumption that at the moment, each
sitemap can define *at most one* flow controller as follows:

<map:flow language="JavaScript">
  <map:script src="calc.js"/>
</map:flow>

If you consider that within each sitemap its *already* permissible to
utilize several different pipelines (including different pipeline
implementations).  Then it might make sense to allow the user the
option of setting flow controllers on a per pipeline basis as well.

This idea can be extended to include something like
'pipeline flowmap chaining': where if the function/continuation
is not available at the pipeline-level,
then flow control is deferred to the sitemap.

To illustrate, here is what a sitemap.xmap
using pipeline-level flow could look like:

<!-- Define available flows for this sitemap  -->
<map:flow language="JavaScript">
  <!-- Note: a "default" sitemap flow is not mandatory -->
  <map:script src="default.js" name="default-flow" default="true"/>
  <map:script src="specific.js" name="specific-flow"/>
</map:flow>

<map:pipelines>

  <!-- this pipeline would use the default flow -->
  <map:pipeline>
  <map:match pattern="Kont/*">
    <map:call continuation="{1}"/>
  </map:match>

  <map:match pattern="login/">
    <map:call function="login"/>
  </map:match>
  </map:pipeline>

 <!--
     this pipeline would use the specific flow
     which might override some of the behavior
     of the default flow
  -->
  <map:pipeline flow="specific-flow">
    <map:match pattern="myKont/*">
      <map:call continuation="{1}"/>
    </map:match>

    <map:match pattern="mylogin/">
      <map:call function="mylogin"/>
    </map:match>
  </map:pipeline>

</map:pipelines>

What does the mailing list think?

I don't think there's a good reason for this complexity. Do you have a good use case for such a usage?

Since the scripts and the functions defined within are visible at the sitemap level, why not simply directly call the specialized functions from the second pipeline? Do you really need the two scripts to not share anything between them?

If no one sees any problems with the above, then I would be
happy to volunteer to implement this.

If you really want to spend some time on the flow layer, I would rather like you spend some time working on some of the items in the TODO file in src/java/org/apache/cocoon/components/flow/. The thread to expire continuations would be a very good first task.

Best regards,
--
Ovidiu Predescu <[EMAIL PROTECTED]>
http://webweavertech.com/ovidiu/weblog/ (Weblog)
http://www.geocities.com/SiliconValley/Monitor/7464/ (Apache, GNU, Emacs ...)


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