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From Adrien Guillon <>
Subject [RT] Design Alternatives To XPath Selectors?
Date Fri, 28 Apr 2006 20:27:33 GMT
   Hello All,

   I have researched previous discussions related to "pipe-aware selectors" 
and XPath selectors within the pipeline.  I realize that there are good 
arguments for and against adjusting a pipeline based on its content  However, 
not being able to select a course of action based upon stream content limits 
Cocoon's usefulness in some application areas.

   It would be nice if I could pass a command handler in Coocon a snippet of 
XML, and have it execute an arbitrary action based on its content.  For 
example, a master RPC handler that takes all RPC calls and routes them where 
appropriate.  This conceptually could make Cocoon polymorphic.  Imagine 
something where all RPC requests are passed to "rpchandler".  This 
"rpchandler" pipeline then peeks inside the request, and routes to a pipeline 
called {1}/handler, where {1} is the URI that should handle the command 

   Imagine sending Cocoon a command snippet in XML like this:


   The snippet could be sent to a master handler and then that pipeline could 
forward the XML package to cocoon://do/something/handler.  That pipeline is 
then responsible to dealing with the request, and returning whatever result 
set was asked for... maybe it's a recipe for cookies, or an image, or a list 
of songs.  The real advantage is that all commands can be handled via the one 
pipeline.  Yes, we could solve the problem using many different matchers... 
but really it would be more flexible in design if we pass all calls to the 
one pipeline which delegates the tasks appropriately.  Then any software 
integrating with Cocoon just has to know the one URI for the request handler.

   I cannot see any way to do something like this in Coocon currently.  Please 
let me know if there is a different approach.  However something that could 
peek inside the data content running through the pipeline would be greatly 

   Whenever  I look at cocoon, I think to myself of OOP but using XML trees to 
push data around into pipelines to process and return results.  I know I'm 
pushing the limits of what Coocon is really designed to do, but ideally 
Cocoon could be a really neat way of tying many webservices together into one 



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