Re: [soa-rm] Semantic Meaning of Message

[Ken Laskey <klaskey@mitre.org>]

Thus we need the capability for an entity to invoke a service, to  
receive the results of that invocation back (e.g. some data, some  
report on a change of state, some response about the extent to which  
the request was satisfied), and to be informed if the invocation failed  
in some standard way (that the invoked service could respond with a  
standard fault message) or in a way that the infrastructure needed to  
intercede. What architectural pieces does this imply?  I would see
- a mechanism to generate a request,
- a mechanism to carry the request to the service,
- a service mechanism to receive the request,
- a mechanism to generate a response (per request or fault),
- a mechanism to carry the request back,
- a mechanism to receive the response,
- a mechanism to monitor that a request and/or response has entered the  
"carry" mechanism and intercede in case of fault within that mechanism.

Now you can say that we assume some of that exists outside the SOA we  
will define, but you've got to say it!

What other patterns (e.g. I need to find a certain type of service)  
imply what other needed mechanisms?

Ken

On Mar 31, 2005, at 7:54 AM, Vyas, Neeraj wrote:

>
> With respect to the question -- If "message" is too "concrete", what is
> the abstraction?
>           I think abstract concept could be Service Request, Service
> Response and Service Fault. So in any case service consumer will send
> the request to actual service to consume it and would accept a response
> from it, or in case of failure of service execution it would except the
> cause of it (fault information). So in my opinion while defining a SOA
> reference model we need to define what request/response/fault model one
> should use. Concrete concept can be Message, Event, Input/Output
> Parameters, Exceptions, etc. based on the communication channel one is
> using. Service can be defined as Request only or Request-Response, this
> information can be collected from the service meta model.
>
>
> Thanks and Regards
> Neeraj Vyas
> CA Computer Associates
> neeraj.vyas@ca.com
>
> -----Original Message-----
> From: Gregory A. Kohring [mailto:kohring@ccrl-nece.de]
> Sent: Thursday, March 31, 2005 2:11 PM
> To: soa-rm@lists.oasis-open.org
> Subject: [soa-rm] Semantic Meaning of Message
>
> Hi,
>
> OK, I have looked at all three examples Duane gives and found that
> while none of them explicitly use the term "message", they all
> define concepts which have a similar semantic meaning.
>
> The RCS reference model, for example, uses the word "event" in much
> the same way an web service person would use the word "message".
>
> The OSI reference model is concerned about communication protocols
> and how they interact. It does not use the word "message", but does
> talk about exchanging "data" between protocols.
>
> The ITA reference model, again does not use the word "message", but
> does use the word "protocol" in a way which can be interpreted as a
> "message exchange pattern".
>
>
> So, while these reference models do not use the word "message", they
> do use terms denoting a similar concept.
>
>
> If "message" is too "concrete", what is the abstraction?
>
>
> Several posters have suggested that some form of "communication" is
> implicit in the definition of a service and therefore does not have
> to be explicitly mentioned.  But doesn't this go against the idea of
> building a reference model?  Shouldn't a reference model explicitly
> define all of its elements?  I would argue that anything which is not
> an implementation detail should appear in the reference model. (How
> you implement the message is an implementation detail, but not the
> concept of the message itself.)
>
>
> Cheers,
>
> Greg
>
>
> --  
> ======================================================================
> G.A. Kohring
> C&C Research Laboratories, NEC Europe Ltd.
> ======================================================================
>
>
------------------------------------------------------------------------ 
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Ken Laskey
MITRE Corporation, M/S H305     phone:  703-883-7934
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