Re: [sca-assembly] ISSUE 16: Component URI is not well described ---Proposal for Aliases

I agree that the uri attribute would
not be needed on component or service.  I think it should be allowed
(at the assembly level) on bindings for both references and services.  Its
meaning when used in these contexts would be defined by the relevant binding
specifications.  See the proposal that I just sent out for Issue 16
and binding URIs.

    Simon

Simon C. Nash, IBM Distinguished Engineer

Member of the IBM Academy of Technology

Tel. +44-1962-815156  Fax +44-1962-818999

David Booz <>

02/07/2008 20:42

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cc

Subject

Re: [sca-assembly] ISSUE 16: Component
URI is not well described --- Proposal for Aliases

This works for the use cases I had in mind.

Though you didn't mention it, I think we wouldn't need the uri attribute
on

component any longer (it could be removed from the current proposal) nor

would we need it for services or bindings on services (this will raise
some

eyebrows).  Bindings on references would still need something in order
to

address services at hardcoded address.

Dave Booz

STSM, BPM and SCA Architecture

Co-Chair OASIS SCA-Policy TC

"Distributed objects first, then world hunger"

Poughkeepsie, NY (845)-435-6093  or  8-295-6093

e-mail:

                    
                     
                     
          

             Mike Edwards      
                     
                     

             <mike_edwards@uk.  
                     
                    

             ibm.com>      
                     
                     
To 

                    
                  "OASIS
Assembly"                
   

             07/01/2008 10:16    
     <> 

             AM        
                     
                     
    cc 

                    
                     
                     
          

                    
                     
                     
  Subject 

                    
                  [sca-assembly]
ISSUE 16: Component  

                    
                  URI is not
well described ---       

                    
                  Proposal
for Aliases                

                    
                     
                     
          

                    
                     
                     
          

                    
                     
                     
          

                    
                     
                     
          

                    
                     
                     
          

                    
                     
                     
          

Folks,

At the F2F meeting, when Issue 16 was discussed, it became clear that there

was a requirement for there to be what

I described as "Aliases" for the structural URIs for a component.

A short reminder of the context for this discussion.

The latest proposal for Issue 16 treats the Component URI as effectively
a

structural URI - the URI describes the place

of a given component in the Domain, starting at the Domain level component

and, where a component is implemented

by a composite, tracing downwards from the domain level through each

"nested composite", adding in the name of

the component at each level.  Where a given composite is used as an

implementation multiple times by different

components, the components within that composite end up with multiple of

these URIs, one for each "usage instance".

So far so good.

These structural URIs can be used for a number of purposes.  Concentrating

on their use for administration and management

purposes, it is required that a given component instance can be given a
URI

which does not change even if the structure of

the artifacts in the domain does get changed.

I term this "unchanging" URI a "URI Alias" - effectively
it is a "fixed"

URI that maps to a specific structural URI - a kind of Map.

Where should these "URI Aliases" be declared and what data should
they

contain?

In my opinion, these URI Aliases should be declared at the Domain level
-

in a Definitions file, for example.  It is hard to make

Aliases work well if the data is inside the composites that might be

reused, since it is hard to make them aware of the multiple

uses of a composite as an implementation.

So a simple idea is to create an <alias/> element which would live
inside a

<definitions/> element (logically at the Domain level)

<alias aliasURI="xs:string" actualUri="xs:string"/>

- this is a simple mapping from the (unchanging) aliasURI to the actual

structural URI of some component - if the component moves)

due to some deployment activity, the aliasURI remains unchanged and stable,

but the actualURI needs updating to point to the new

location of the component.

Yours,  Mike.

Strategist - Emerging Technologies, SCA & SDO.

Co Chair OASIS SCA Assembly TC.

IBM Hursley Park, Mail Point 146, Winchester, SO21 2JN, Great Britain.

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