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Subject: RE: [soa-rm] Definition(s) of "service"


I see there is a large thread on this....so this may be outdated by the
time I plow through the whole thing.  Nevertheless, comments below.

-Rebekah
> -----Original Message-----
> From: Ken Laskey [mailto:klaskey@mitre.org]
> Sent: Wednesday, July 27, 2005 5:14 PM
> To: Chiusano Joseph; soa-rm@lists.oasis-open.org
> Subject: RE: [soa-rm] Definition(s) of "service"
> 
> The service primarily accesses behaviors of others.  
I don't believe that a service *accesses*.  I believe it is more correct
to say that a service *offers*.  (Having now read ahead, I think it
appropriate to say a service "carries out."  Carries out seems to be
about the transformation of a service offer into the effect it offers.
It sounds like we're trying to capture the essence of both sides of that
potential v actual duality and recognize they are intertwined to some
degree.)

Behaviors
> associated with the service are the policies and effects included in
> its service description.
> 
I read this to say that behavior does not represent in the service
description.  What about the behavior required to actually cause the
effect?

I suspect you are differentiating between operational and functional
behavior, and if that is the case, I agree with the partition between
policy and description.

Rebekah

> Ken
> 
> At 05:06 PM 7/27/2005, Chiusano Joseph wrote:
> > > Duane suggests: "A service is an abstract action boundary to
> > > a set of behaviours or the observable result of some
functionality."
> >
> >Rather than think of a service as a boundary to something, can it
also
> >be thought of as an entity that encapsulates (or "carries out") a set
of
> >behaviors?
> >
> >Joe
> >
> >Joseph Chiusano
> >Booz Allen Hamilton
> >O: 703-902-6923
> >C: 202-251-0731
> >Visit us online@ http://www.boozallen.com
> >
> >
> > > -----Original Message-----
> > > From: Duane Nickull [mailto:dnickull@adobe.com]
> > > Sent: Wednesday, July 27, 2005 5:04 PM
> > > Cc: soa-rm@lists.oasis-open.org
> > > Subject: Re: [soa-rm] Definition(s) of "service"
> > >
> > > Perhaps combining all of these is closer to the answer:
> > >
> > > Duane suggests: "A service is an abstract action boundary to
> > > a set of behaviours or the observable result of some
functionality."
> > >
> > > I would want to refrain from mentioning any actors such as
> > > provider, consumer, participant in this definition since we
> > > may define those later by referring to service (avoidance of
> > > circular references). I used the word "abstract" specific to
> > > our RM. In an RA, it may be a more concrete action boundary
> > > (see Microsoft def. below).
> > >
> > > More definitions of services:
> > >
> > > W3C says: "A Web service
> > > <http://www.w3.org/TR/ws-arch/#service> is an abstract notion
> > > that must be implemented by a concrete agent
> > > <http://www.w3.org/TR/ws-arch/#agent>." (Thank you W3C. I am
> > > more confused now. Next!)
> > >
> > > Microsoft says: "A software entity whose interactions with
> > > other entities are via messages. Note that that a service
> > > need not be connected to a network." (too concrete but good
> > > for RA. I wonder why they felt compelled to point out that it
> > > need not be connected to the network to be a service. This is
> > > in alignment with our notion of "a service is a service, even
> > > if not invoked" so I like that part.)
> > >
> > > CISCO says: "A group of related functions (or operations)
> > > that work together to provide a functional capability."
> > > (interesting but does really state what a service is, just
> > > what it represents).
> > >
> > > The US EPA says: "Breeding, the deposition of boar semen into
> > > the female." (Hmmm - probably not useful - let's leave this one
alone)
> > >
> > > DOI says: "A defined result from a defined action ie, do X
> > > and the result will be Y. Services perform functions when
> > > invoked into action."
> > > (paraphrased slightly. Too concrete but interesting)
> > >
> > > Apple says: " A service is an I/O Kit entity, based on a
> > > subclass of IOService, that has been published with the
> > > registerService method and provides certain capabilities to
> > > other I/O Kit objects. In the I/O Kit's layered architecture,
> > > each layer is a client of the layer below it and a provider
> > > of services to the layer above it. A service type is
> > > identified by a matching dictionary that describes properties
> > > of the service. A nub or driver can provide services to other
> > > I/O Kit objects."
> > >
> > > I liked part of the latter analogy about the layering - being
> > > a slave to the entity above it while being a client of the
> > > entity below it. This effectively addresses the concept of
> > > service context. In one context, something is a service
> > > consumer while in another it is a service provider. The
> > > definition is far to specific to Apple but is useful to
> > > expand thinking.
> > >
> > > To continue extrapolating from Ken's ramblings, "Two things
> > > are needed to effectively use a capability under SOA:
> > > - understanding the underlying capability;
> > > - understanding the accessing service."
> > >
> > > I fundamentally think that all that is really required is an
> > > understanding of the behavioural aspects of the service, the
> > > data model the service uses, the other metadata and the
> > > policies of the service.
> > >
> > > Duane
> > >
> > > >
> > > >
> > >
> 
> --
>
--------------------------------------------------------------------
> -------------
>    /   Ken
> Laskey
\
>   |    MITRE Corporation, M/S H305    phone:  703-983-7934   |
>   |    7515 Colshire Drive                    fax:      703-983-1379
|
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/
>
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> 



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