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From Anoop Aryal <>
Subject retaining data from a partial pipeline for subsequent requests
Date Wed, 18 Jun 2003 16:52:24 GMT
i'm evaluating cocoon to see if it suits our needs. i've used fop
extensively before. and i know just enough of cocoon to be dangerous.
this is kinda long but i put a lot of time in drawing in ascii to make
it clearer; hopefully ;)

the problem:

in keeping with the SOC, i have the following setup:

Generators:        A          B          C          --|
                   |          |          |            |- the data layer
                   -----------------------            |
                              |                       |
Aggregation:                  D                     --|
Transformation:               E                     ---- the 
                              |                          business logic
                   --------------------------       --|
                   |        |        |      |         |- the prettfying 
Formatting:       rtf      xsl      pdf    html     --|  layer

in the html, i refer to images (charts, which i'm generating using Fins)
that are generated according to the data generated at E. But as they are
subsequent requests from the browser don't have access to the data since
the pipeline that generated the data was done and over with after
generating the html. So, i'm left with two options:

i) regenerate the data up to E:

Generators:        A          B          C          --|
                   |          |          |            |- the data layer
                   -----------------------            |
                              |                       |
Aggregation:                  D                     --|
Transformation:               E                     ---- the 
                              |                          business logic
                            jpg/png                 ---- the prettfying

ii) save the data from the pipeline into the session (from A, B, C) when
generating the html and use that as such:
Generator: F (reads data from the session previously set by A,B,C) and
generates xml to feed into the fins transformer. 

Current solution:
as option (i) would require me to regenerate the dataset, i opted to use
option (ii). but then, since i can only shove the data into sessions
from an xsp (?) i only have the raw form of data from (A, B, C) in the
session. F would then have to do what D and E does. complete breakdown
of SOC.

Wishful/hopeful thinking:
something like this would be optimal:

Generators:        A          B          C        
                   |          |          |        
Aggregation:                  D                   
Transformation:               E ----------------- tee* --          
                              |                          |
                   --------------------------            |
                   |        |        |      |            |
Formatting:       rtf      xsl      pdf    html**        |
                                     formatted as a png/jpg/svg and
                                     stored in cocoon cache using a
                                     unique key** for the subsiquent 
*) tee as in make a copy and pass one copy to the html formatting step.
and another to the image formatting step.
**) the key would be predetermined so that the src element in the html
would know which image url to put in. and another pipeline would deal
with requests for images keyed off this way.

(That does sound out of wack. told you, i know enough to be dangerous)

So, the question is, how do you generate images that are referenced by
some html when the images are another view of the data that the html is
displaying without regenerating the data for the image generation?

thanks in advance,

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