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From Gianugo Rabellino <gian...@apache.org>
Subject Re: [RT] Sitemap inheritance
Date Sun, 26 Oct 2003 17:21:45 GMT
Stefano Mazzocchi wrote:
>> Probably I should be more aware of what kind of inheritance exactly 
>> block introduce in your design.
> I might be wrong, but I think that the current block inheritance 
> mechanism does exactly what you were describing in your previous emails.
> 
>> So far I haven't been able to find anything explicitly oriented to 
>> pipeline reuse/inheritance: it's pretty clear that components 
>> (classes) will be inherited, and the same goes for resources, but what 
>> about pipelines?
> 
> I'm not sure we are using the same terminology here. but let me give you 
> an example of how the blocks will work:

[...]

As long as there is room for overriding, i.e.:

  block a

   ...
   <pipeline>
    <match pattern="*.html">
     ... do something ...
    </match>
   </pipeline>
   ...

  block b extends block a

   ...
   <pipeline>
    <match pattern="*.html">
     ... do something different ...
    </match>
   </pipeline>
   ...

I'm fine with it. *But*, again, this is a block-only behaviour (works as 
long as you have two blocks).


>> To me, having inheritance only in blocks look a bit like saying that 
>> you can extend only from java.*, while user classes have to be always 
>> final. It's rough and inaccurate, but can you see my point?
> 
> 
> hmmm, not really. blocks are application level components that isolate 
> your logic. this is exactly what you are going to need. it would be like 
> saying that object orientation is overkill for datatypes and nothing is 
> wrong with C unions.
> 
> I do agree that it looks like overkill to come up with a block for your 
> own stuff that you need to inherit, but i think that this will force you 
> to define contracts betweeen stuff and this will help you later on (just 
> like OOP datatypes vs. unions)
> 
> but, supposing for a second we allow sitemap inheritance without blocks, 
> how would you make it work for both?

I guess that once you have pipeline inheritance, it would be easy enough 
to have it working both on blocks and on "ordinary" user configurations. 
But my strongest point is that Cocoon has a steep learning curve 
already, and while I do foresee some benefits in having *everything* 
packaged as a block, I still think that there should be room for 
traditional (=sitemap on filesystem) Cocoon development.

This is also good for development: if the cycle becomes "edit 
sitemap->package as block->install in cocoon->fail->retry" I guess it 
would just be too heavy for users.

Keep in mind that we should account for non-Java savy users too, people 
who might be uncomfortable in using jar techniques, edit metafiles, 
running ant and so on. Today all that is required to run Cocoon is XML 
knowledge and a text editor: if everything becomes a block, Cocoon will 
remain just a Java-developer-centric application.

In short: blocks should ease a Cocoon developer's life, and block 
assembling should belong to the "programmer" domain. Normal users should 
see only benefits from it. Or am I wrong?

Ciao,

-- 
Gianugo Rabellino
Pro-netics s.r.l. -  http://www.pro-netics.com
Orixo, the XML business alliance - http://www.orixo.com
     (Now blogging at: http://blogs.cocoondev.org/gianugo/)


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