Re: [merlin] Block assembly question.

[Stephen McConnell]

Daniel Krieg wrote:

<snip/>
 

 <component name="fred" class="MyComponentClass">
   <dependencies>
     <dependency key="my-key">
       <select>
         <feature key="name" value="george" match="required"/>
       </select>
     </depedency>
   </dependencies>
 </component>
What the above is basically saying is that for the dependecy declared
under "my-key", the assembly system would be required to select a
candidate with a matching name.
How does this sound?
   

<snip/>

<select/> seems useless -- what else could you do? 

Quite a bit actually. 
Instead of locking in on the selection by name, you would be able to 
describe quality-of-service criteria.

Consider this...

<component name="george" class="MyComponentClassA"/>
<component name="henry" class="MyComponentClassA"/>
<component name="fred" class="MyComponentClassB">
   <dependencies>
       <dependency key="my-lookup-key-1">
           <feature key="name" value="george" match="required"/>
       </dependency>
       <dependency key="my-lookup-key-2">
           <feature key="name" value="henry" match="required"/>
       </dependency>
   </dependencies>
</component>
...and since the name-binding of a service is not REALLY a feature of the
service, perhaps...
<component name="george" class="MyComponentClassA"/>
<component name="henry" class="MyComponentClassA"/>
<component name="fred" class="MyComponentClassB">
   <dependencies>
       <dependency key="my-lookup-key-1" provider="george"/>
       <dependency key="my-lookup-key-2" provider="henry"/>
   </dependencies>
</component>
Problem here is that it would lock us into selection by name.  Instead I 
want something more generic.  Consider the following:

 <component name="george" class="MyComponentClassA"/>
 <component name="henry" class="MyComponentClassA"/>
 <component name="fred" class="MyComponentClassB">
   <dependencies>
       <dependency key="my-lookup-key-1">
           <feature key="supplier" value="ASF" match="optional"/>
           <feature key="name" value="henry" match="exclude"/>
       </dependency>
       <dependency key="my-lookup-key-2">
           <feature key="name" value="henry" match="required"/>
       </dependency>
   </dependencies>
 </component>
In the above scenario, I can influence the selection process based on 
attributes.  This means I can use QoS parameters to drive the selection 
process.  This covers both selection by name and selection by QoS.

Basically you get what you want (selection by name) and I get what I 
want (selection by attribute matching).

Steve.

--

Stephen J. McConnell
mailto:[EMAIL PROTECTED]
http://www.osm.net
Sent via James running under Merlin as an NT service.
http://avalon.apache.org/sandbox/merlin


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