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From Geoff Howard <>
Subject Re: Ant/Maven/Centipede discussion
Date Wed, 08 Oct 2003 02:18:19 GMT
Stephen McConnell wrote:
> Geoff Howard wrote:
>> If you havn't read up on the blocks docs on the wiki lately (the last 
>> two weeks) you really should.  Stefano has put a good series of pages 
>> up detailing the plan and the current implementation ideas. 
> Another followup question related to the following note on the wiki:
>    * dependencies:
>          o the URI(s) of the blocks on which this blocks depends on
>            (optional)
> I'm thinking about this relative to Avalon Merlin Block dependencies.  
> Under Merlin a block dependency is implicit - not explicit.  By implicit 
> I mean that you can establish the dependencies that a blocks has 
> relative to the computational dependencies that the blocks 
> implementation exposes.  This means that a deployment system (tool or 
> container) can resolve dependencies at runtime, using (a) locally 
> available resources, (b) external repositories, or via more complex 
> means (roadmap stuff) using (c) a remotely accessible service provider, 
> or (d) remotely provided serialized block descriptions.

And as I see it and understand it - it must be this way because a Cocoon 
block as envisioned so far employs a "weak typing" in some of the 
"services" (maybe better expressed as "behavior") it exposes.  The 
reason services is in quotes is that they are not Avalon Services but 
weakly (intentionally) defined resources.  For example, an xsl (though 
currently it is required that this be exposed via a pipeline).  Clearly 
in that case all the explicitness of java that makes computational 
dependencies possible is out the window and you have to fall back on 
some rude indentifier for a generalized block "behavior".

By the way, I think you and Stefano were misunderstanding each other 
over the description of this issue.  When he was describing blocks as 
"functional" units you seemed to read that more as "function_ing_" 
(i.e., 'they work' or 'self-contained').  I think he was describing this 
generalized behavior aspect.

Now, a major question in the back of my mind is whether this generalized 
behavior contract can be represented (implicitly from a block 
developer's standpoint) via an Avalon Service which may make 
Avalon/Merlin blocks closer to Cocoon blocks than they seem at present.

Having said that though, I definitely resonate with the need to get 
going.  I feel the best way forward is to look for true synergy (either 
present or future) in the implementation phase without bogging down.

> What I have not resolved in my head yet is how the dependency url for 
> cocoon blocks translate to computational descriptions (or to put this 
> into Merlin terms, how can I translate a cocoon block uri into 
> computation service request that could be used in Merlin to return a 
> serialized Merlin block descriptor)?

I am not sure I have wrapped my head around the parallel universe to 
even understand the question.  Ever see the Seinfeld where they meet up 
with the "bizarro" parallel Seinfeld/Kramer/George?

I have read through the Merlin docs you pointed to and plan to start 
playing with it some.  I've also started looking into James in part so I 
can understand its move from Phoenix to Merlin.  (By the way, does 
anyone know why in the world does that not have a more functional 
listserv?  It doesn't seem that hard to implement with what's already in 
place.  Have I missed some complexities or has it just never itched 
anyone enough?)


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