RE: [soa-rm] FYI: BEA SOA Reference Diagram

["Christopher Bashioum" <cbashioum@mitre.org>]

Two points:

1) in our document, we make the assertion that a service is the fundamental
building block of an SOA.  If that is correct (and I believe it is), then
you cannot have an SOA with only 1 building block.  The concept of a service
being the fundamental building block of an SOA implies rather strongly that
the relationship among multiple services (and the possible specialization of
services) is part and parcel of an SOA.  In other words, there is something
important to how these building blocks get put together that is inherent in
SOA.  Not sure what that is just yet, and maybe we can show that in a single
stack.

2) I am not sure about the sufficiency of Ken's statement.  I think there is
something about the orientation applied when building a service description
that gets to the re-purposing.  I.e., building a service with the stated
requirement of re-purposing of that service.

Having said #2, I am not sure if that is really an essential property of
SOA, or if it is a quality of a "good" SOA.



-----Original Message-----
From: Duane Nickull [mailto:dnickull@adobe.com] 
Sent: Wednesday, May 18, 2005 2:06 PM
Cc: SOA-RM
Subject: Re: [soa-rm] FYI: BEA SOA Reference Diagram



Ken Laskey wrote:

> The essence of a SOA is multiple services coming together to satisfy a 
> set of needs.

This is the core point we have not reached consensus on yet.  This is a 
well worded as can be so I would like to use this assertion as a basis 
for the discussion.

Thoughts:

I would agree that "The essence of a SOA infrastructure is multiple 
services coming together to satisfy a set of needs.  I do have 
reservations about the concept of multiplicity of services being used as 
a key metric to define SOA.

Questions:
1. Is it necessary that there be more than one service in order that SOA 
be SOA? 
2. If yes to #1, is it necessary to call services only in sequence?

My gut feeling is that having multiple services is probably a given for 
any specific implementation of SOA, however it is not a requirements for 
something to be service oriented.  If I architect one application and 
build it with a single service, service description, policy set, (+ 
whateverElseGetsInTheReferenceModel), is that service oriented 
architecture?  I think yes.

I would fully support a reference architecture depicting multiple 
services  being used either sequentially or in parallel, however think 
that is a sub project best left for a dedicated sub committee.

Duane

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