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   RE: [xml-dev] SOA and the Single URL

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Ah - now I see where you're going. Yes, a "dispatcher" service can
categorized in three ways: 

(1) a "composite" service, (2) a "coordinator" service, or (3) a
"process" service.

With (1), multiple services are invoked as needed by a "primary" (for
lack of a better term) service. This is a classic case in which - for
example - a primary service invokes another service to execute some
calculation, and the result is returned to the primary service.

With (2), a service (called a "coordinator" service) whose sole mission
is to coordinate the interactions among multiple other services as part
of a single activity exists. This coordinator service is more of an
"infrastructure"-type service in that it is not carrying out domain- or
application-specific functions. An example of an emerging standard in
this area is OASIS WS-CAF (Web Services Composite Application
Framework), while an example of a specification is the combination of
WS-Coordination/WS-Transaction (with the understanding that
WS-Transaction is comprised of 2 specifications, WS-AT (WS-Atomic
Transaction) and WS-BA (WS-BusinessActivity)). And WS-CAF, given the "C"
in its name, can be considered as category (1) above, although I think
it is more (2) since it is infrastructure.

With (3), the service's functionality, when carried out, actually causes
a state change in one or more resources. That is, inventory may be
reduced, an account may be debited, etc. This is also different from (1)
in that (3) involves orchestration (sequencing of activity steps,
dependencies among services, etc.). An example of a service in this
category would be a Purchase Order service that may be expressed using a
specification/emerging standard such as OASIS WS-BPEL (which is not yet
ratified - but will be soon), or its predecessor BPEL4WS.

Hope that helps--

Joseph Chiusano
Booz Allen Hamilton
O: 703-902-6923
C: 202-251-0731
Visit us online@ http://www.boozallen.com

> -----Original Message-----
> From: Bullard, Claude L (Len) [mailto:len.bullard@intergraph.com] 
> Sent: Thursday, August 04, 2005 12:14 PM
> To: Chiusano Joseph; xml-dev@lists.xml.org
> Subject: RE: [xml-dev] SOA and the Single URL
> Too bad.  You missed a really fine party and a really bad war.
> The question is a good one.  Services.  In some approaches, a 
> single service may be acting as a dispatcher to other 
> services and the SOA is only exposing the one to the world. 
> len
> From: Chiusano Joseph [mailto:chiusano_joseph@bah.com]
> Sorry - I was born in the late 60s;)
> > but the
> > question is, given an Enterprise Service Bus and an SOA, should one 
> > use a single URL to identify multiple processes?
> > Yes, I know what a dispatching service is, but given REST 
> vs SOA, what 
> > do you think the consequences of a single URI approach are?
> Sorry Len, not following you 100% here - are you referring to 
> run-time processes, or separate services?


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