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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