A
few contextual comments and questions inline. I typed these originally on Friday night before
the thread of conversation spun out with some other members of the SOA-RM on
this mailing list. However, I think my comments below still apply.
Rebekah
Rebekah Metz
Associate
Booz Allen Hamilton
Voice: (703) 377-1471
Fax:
(703) 902-3457
-----Original Message-----
From: soa-forum-bounces@xxxxxxxxxxxxxx [mailto:soa-forum-bounces@xxxxxxxxxxxxxx]
On Behalf Of Andras Szakal
Sent: Friday, May 05, 2006 9:50 AM
To: Chris Harding
Cc: Service-Oriented Architecture CoP; soa@xxxxxxxxxxxxx
Subject: [soa-forum] Re: Definitions of SOA
Team,
I offer this additional
chart which depicts the outcome of our discussion
last week. I am still
working the chart but it's a decent start. We agreed
that SOA is actually only
one aspect of this very interesting industry
initiative that needs our
focus.
<RLM> Although I like the concepts that you’ve related
to the notion of services and SOA, I have a concern that SOA seems to be
considered only as a technology layer concept of a larger concept called
SOA. I would challenge the group to realize instead that SOA is about the
alignment of IT with business. Intuitively, this concept spans the three
layers in the first slide.
As part
of the SOA RM out of OASIS, we initially started down this same path. In
fact, during early drafts of the RM, several members of the TC contemplated
renaming the specification to “Service Reference Model.” In addition, we
spent a significant amount of time working to a description of SOA that spans
these three layers presented - because they are synergistic. (Note that
within the reference model we don’t directly discuss technologies which are
left for Reference Architectures and Implementations).
I think we need to focus on
service orientation as a superset of the SOA
discussion. In fact one
could argue that service orientation may be
implemented by a combination
of architectural styles and not just SOA/web
services.
I’d be
interested in hearing about what other architectural styles fit the bill.
(See attached file:
Service_Orientation_Def_v1.ppt)
<Stepping
onto my soapbox>
The
notion that a service is a “thing” which is separate from a capability that is
served is incorrect. A service is an event. It is not separate from
a capability. It is the performance of that capability by some entity
(service provider) for some other entity (service consumer). Although it
is easy to think about the concept of service in terms of ‘things’; in actuality,
this concept unifies both active and thing. In the same vein, it is a red
herring to think about SOA as technology only.
In
Slide #2, the discussion of service orientation maps nicely to the treatment of
needs and capabilities as part of the SOA Reference Model. The difference
is that this definition seems to treat service orientation separately from the
core definition of SOA. Instead, brining together needs and capabilities
is of the essence in SOA, an integral part.
The
definition of service speaks of a black box. With this definition, I
would ask what is the role of a service description? Does the existence
of a service interface, and the inputs/outputs with which service interactions
occur part of the black box?
I don’t understand why
the final two bullets, namely “Requires strong governance of service
representation and implementation” and “Requires a ‘Litmus Test’, which
determined a ‘good services’ are part of the definition? Who decides
“good” vs. “bad” services?
Rebekah
Regards,
Andras
Andras Robert Szakal
Chief Architect IBM Federal
Software Group
Distinguished Engineer &
Senior Certified IT Architect
Member Open Group Board of
Directors
Tie Line: 930-9215
External Line: 202-595-1678
text message: andras1@xxxxxxxxx
email: aszakal@xxxxxxxxxx
Chris
Harding
<c.harding@opengr
oup.org>
To
Service-Oriented
Architecture CoP
05/05/2006 08:31 <soa-forum@xxxxxxxxxxxxxx>,
AM
"'Service-Oriented Architecture
CoP'" <soa-forum@xxxxxxxxxxxxxx>
cc
soa@xxxxxxxxxxxxx
Subject
Definitions
of SOA
Hi -
As a further update, here is
the definition of SOA that was presented at
The Open Group conference
last week (and which we have shared with the
OMG).
SOA is an architectural
style that supports service orientation
•Service orientation
A way of a way of thinking
in terms of services and service based
development and the outcomes
that services bring
•Service
A logical representation of
a repeatable business activity that has a
specified outcome (e.g.,
check customer credit; provide weather data,
consolidate drilling
reports), is self-contained and maybe composed of
other Services. It is a
black box to consumers of the Service
•Architectural Style
The combination of
distinctive features in which Enterprise Architecture is
done, or expressed
•The SOA Architectural
style’s distinctive features:
– Based on the design
of the services comprising an enterprise’s
(or
inter-enterprise) business processes. Services mirror real-world
business activity
– Service
representation utilizes business descriptions. Service
representation requires providing its context (including business
process, goal, rule, policy, service interface and service component)
and
service orchestration to implement service
– Has unique
requirements on infrastructure. Implementations are
recommended to use open standards, realize interoperability and
location transparency.
– Implementations are
environment specific, they are constrained or
enabled
by context and must be described within their context.
– Requires strong
governance of service representation and implementation
– Requires a “Litmus
Test", which determined a “good service”
At 20:31 04/05/2006, Cory
Casanave wrote:
As an update from the OMG meeting last week, the SOA SIG adopted the
following definition of SOA;
Service Oriented Architecture is an architectural style for a
community of providers and consumers of services to achieve mutual
value, that:
Allows participants in the communities to work together with
minimal co-dependence or technology dependence
Specifies the contracts to which organizations, people and
technologies must adhere in order to participate in the
community
Provides for business value and business processes to be
realized by the community
Allows for a variety of technology to be used to facilitate
interactions within the community
The corresponding definition of service has not yet been finalized
but the sense of the group is that there would be both a
business/domain centric notion of service as well as an interaction
focused definition.
In both cases this seems to fit well with the notion of SOA that is
evolving in this group and in the SOA Demo.
Regards,
Cory Casanave
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Chris
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