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Subject: ISSUE 16: Component URI is not well described --- Proposal for Aliases


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.
Phone & FAX: +44-1962-818014    Mobile: +44-7802-467431  
Email:  mike_edwards@uk.ibm.com

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