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From Stephen McConnell <mcconn...@osm.net>
Subject Re: Fresh Outlook: (was RE: [desperate plea] RE: The need for 'hints')
Date Tue, 25 Jun 2002 21:17:59 GMT


Robert Mouat wrote:

>Robert Mouat wrote:
>
>  
>
>>Leo Sutic wrote:
>>
>>    
>>
>>>Robert,
>>>
>>>we all agree.
>>>      
>>>
>>ok, I got a bit paranoid that metadata was going to replace the job of the
>>assembler.
>>    
>>
>
>re-reading some of the recent emails - I think I get it now - the
>difference is between blocks and components:
>
>  - a block is a component with metadata.
>  
>

My take ...
A component is an object that implements a licecycle policy.  A 
component may expose the lifecycle contract through metadata and other 
means.  Certain containers will enforce a formal comonent contact. 
 Phoenix is a container that uses a meta-model described through a 
constuct called a block.  This formal structure can be considered to be 
the original formal-component defintion.

>  - when lookup(roleName) is called:
>
>    - if the client comes with no metadata specifying the meaning of the
>    roleName, then the component/block returned is the one specified by
>    the assembler.
>

When a client invokes lookup, the result returned (today) is completely 
an implementation issue for a container. Assurance concerning the 
semantics of lookup on a component manager are insufficiently defined 
today.  You go to the documentation of the container you are using, and 
look for information about the semantics and assumptions that the 
contaer applies to the lookup opertion.  In the future, I hope that this 
will be eliminated and that we will be able to provide a formal contract 
from client, through lookup, to container - and in that specification, 
define how varients of the formal process can be handled in a consistent 
way.

>
>    - if the client has metadata that specifies the meaning of the
>    roleName then the container compares this with the metadata for the
>    blocks and returns one that matches.  [aside: I assume that the
>    assembler can overide this]
>

Metadata instructions do not define the routing of a supplier componet 
to a dependent component.  This is the resonsibility of the assembler. 
 Certtain contains can fill in missing information and make the process 
easier for the assembler.  For example, in the absence of an explicit 
assembly directive, Merlin will attempt to automatically complete the 
routing of the entirte dependency chain.


>
>is this correct?
>

Yyyyyyyy ... es.


>
>sorry for taking up so much bandwidth trying to figure this out.
>

Ce cool!

Cheers, Steve.

>
>Robert.
>
>
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>
>  
>

-- 

Stephen J. McConnell

OSM SARL
digital products for a global economy
mailto:mcconnell@osm.net
http://www.osm.net




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