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

[Mike Edwards <mike_edwards@uk.ibm.com>]

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

---

Unless stated otherwise above:
IBM United Kingdom Limited - Registered in England and Wales with number 741598.
Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU