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Subject: SOA-Pro & Core Concepts
Frank and Team,
Ignoring the diagrammatic elements that comprise the UML
Profile part of SOA-Pro for the moment, and just focusing on their definition of
core concepts like "Participants" and "Services," I think we should try and take
the opportunity to be good stewards and harmonize our efforts. Otherwise,
if we go for standardization of our RA and OMG has already standardized on
SOA-Pro, I think we will be doing a disservice to the community of practice out
there if we don't have at least the spirit of alignment.
SOA-Pro defines core concepts as follows:
Service Oriented Architecture - An architectural
paradigm for defining how people, organizations and systems provide and use
services to achieve results.
This seems fairly consistent with our definition in the
RM.
Service - A capability offered by one entity or
entities to others using well defined "terms and conditions" and
interfaces.
Again, more or less consistent with our definition in the
RM.
Participants - Types of actors defined both by the
roles they play in services architectures and the services they provide and
use. Participants can represent software components, organizations,
actors, or individuals.
Slight divergence from our definition in the RA. We of
course do not explicitly define Participants in the RM. Notice the use of "roles!" I think it is critical to get this into
our models, whether we add an additional abstract concept such as "Actor" or
not. Personally, I don't really think we need to add that additional
complexity as long as we cover roles in our Participants
definition.
In addition, in the RA, we distinguish Stakeholders from
Participants.
SIDEBAR QUESTION FOR FRANK: Can you provide an example
of a non-human Stakeholder per our definition of Stakeholder? Yet to be resolved are Agents. While Agents are
described all over the SOA-Pro metamodel section (Part II), I did not see any
formal definition of Agents in Part I of the spec. Actually, not even in
Part II. This is a topic that will require further
investigation.
Services Architectures (or SOA) - A network of
participant roles providing and consuming services to fulfill a purpose.
Puts a set of services in context and shows how participants work together for a
community or organization.
Not explicitly defined in the RM or RA, at least not according
to roles.
Community Services Architecture - A "top level" view
of how independent participants work together for some purpose.
Some elements of this concept in our Social Structure models
in the RA.
Service Contract - Defines the terms, conditions,
interfaces and choreography that interacting participants must agree to
(directly or indirectly) for the service to be enacted - the services contract
is the full specification of a service which includes all the information,
choreography and any other "terms and conditions" of the service.
Seems a little like our notion of Execution Context defined in
the RM, but not quite. Does get at what Michael Poulin has been talking
about. Not yet sure how to deconstruct this as of yet. SOA-Pro does
not call out either Execution Context or Service Contract in Annex B
(Conformance to OASIS RM).
There is some discussion of choreography. They're very
brave to take on this term because of its inherent baggage, but they define it
as follows:
Choreography - A specification of what is transmitted
and when it is transmitted between parties to enact a service exchange.
The choreography specifies exchanges between parties - the data, assets and
obligations that go between the service participants and any other service
interface. (Dave Ellis should like this.)
The discussion on Service Interface is extensive and
somewhat complex so I won't capture it in this e-mail thread.
Participant Services Architecture - A class that is
expected to have its external contract defined in some other portion of the
model, resulting in a port, and its internal composition described using Service
Contracts.
This seems more along the lines of the UML Profile than a core
concept so we should let this one slide for the moment.
Those are the core concepts in SOA-Pro I found.
Perhaps others have found additional ones. In any event, I think it would
be wise to reconcile our differences; particularly with respect to the RA
concepts, which are still in work. The RM remains the guiding
standard for both sets of specs.
Cheers...
- Jeff, JPL
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