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From Stephen McConnell <mcconn...@apache.org>
Subject [RFI] service lookup semantics
Date Tue, 02 Dec 2003 20:50:14 GMT

Unico Hommes wrote:

>Sylvain Wallez wrote:
>> Registering a service consists in registering an instance of 
>> the service interface with additionnal properties that describe 
>> the service. The lookup mechanism then allows to select a 
>> particular implementation of the service depending on property 
>> values, by using a simple LDAP-like query language.
>Hmm, I like this. This is something that is still missing from Avalon
>IMHO: richer service lookup semantics. I've had several instances where
>I needed this.

Currently the metainfo model allows the attribution of properties to a 
service interface, component implementation and/or service 
dependendency.  However - there are two things missing:  (a) 
implementation at the @avalon tag level for attribute addition (which is 
simply a to-do action); (b) defintion of how a query would be supplied 
by a component to the object providing the service (e.g. service manager 
or whatever). Clearly the current ServiceManager interface does not 
provide the flexibility needed - but a lookup key of type Object opens 
up possibilities because we can apply transformations of arguments based 
on metainfo - e.g. an LDAP-like query (or constrain expression, or ...) 
could be transformed into a parameterized lookup which could be 
transfored into a service.

Anyway - that a hint at what's spinning around in my head just at the 

Cheers, Steve.


Stephen J. McConnell

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