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RE: Separate concepts for "service" and "targetResource?" (was RE : /service/@targetResource ?)

From: Katia Sycara <katia@cs.cmu.edu>
Date: Wed, 21 May 2003 21:28:06 -0400
To: Walden Mathews <waldenm@optonline.net>, "Champion, Mike" <Mike.Champion@SoftwareAG-USA.com>, www-ws-arch@w3.org

In Mark Baker's example, the "service" was a "transfer funds service" not an
account changing service. So, the transfer funds service could access the
account information in my bank's database. This database access is not a Web
resource with a unique URI, in that sense it is "private" and not visible to
requesters of the transfer money service. this is what I meant.

-----Original Message-----
From: Walden Mathews [mailto:waldenm@optonline.net]
Sent: Wednesday, May 21, 2003 8:25 PM
To: Katia Sycara; Champion, Mike; www-ws-arch@w3.org
Cc: katia@cs.cmu.edu
Subject: Re: Separate concepts for "service" and "targetResource?" (was
RE : /service/@targetResource ?)


That seems backwards to me.  The "service" is the desired change
to your account.  The account is the resource.  It may be private in
the sense your bank account is [should be] private, but it ain't private
in the sense of private methods and implementation detail.  It's


----- Original Message -----
From: "Katia Sycara" <katia@cs.cmu.edu>
To: "Champion, Mike" <Mike.Champion@SoftwareAG-USA.com>;
Cc: <katia@cs.cmu.edu>
Sent: Wednesday, May 21, 2003 3:20 PM
Subject: RE: Separate concepts for "service" and "targetResource?" (was RE :
/service/@targetResource ?)

> Mike,
>  the "turtle" picture you painted makes a lot of sense.
> As for Mark Baker's concern about the resources that a service changes
> "behind" it, such as accounts that a bank transfer service may change,
> resources are "private" to the service and do not have a URI anyway (as
> as the external world of services is concerned).
>  --Katia
> -----Original Message-----
> From: www-ws-arch-request@w3.org [mailto:www-ws-arch-request@w3.org]On
> Behalf Of Champion, Mike
> Sent: Wednesday, May 21, 2003 2:51 PM
> To: www-ws-arch@w3.org
> Subject: RE: Separate concepts for "service" and "targetResource?" (was
> RE : /service/@targetResource ?)
> > -----Original Message-----
> > From: Ugo Corda [mailto:UCorda@SeeBeyond.com]
> > Sent: Wednesday, May 21, 2003 1:13 PM
> > To: Champion, Mike; www-ws-arch@w3.org
> > Subject: RE: Separate concepts for "service" and
> > "targetResource?" (was
> > RE: /service/@targetResource ?)
> >
> >
> > While examples can be made where a service acts like a facade
> > in front of a physical resource (see the printer example), in
> > the general case no specific "resource", particularly not a
> > "physical" one, can be identified and associated with a
> > service. (The typical example is a Web service that simply
> > uses a bunch of other Web services to come up with its responses).
> >
> > The only "resource" behind a service that I feel I could put
> > my hands on is an agent (a piece of code). But I doubt the
> > proponents of /service/@targetResource were referring to that.
> >
> > Once we go beyond the agent immediately behind the service,
> > all kind of other resources might surface that the agent acts
> > upon.
> Here's my (personal) conception of a way to sort out all the inputs we got
> in Rennes:
> At the very bottom of the stack there is some code that does some real
> in the real world.  For the sake of this discussion, let's say that it's a
> purchase order processing module in an ERP system, or maybe that BPEL
> implementing a loan approval process.  We *could* think of this as a
> "resource" (but that would be a problem because it's identity and state
> not necessarily exposed to the outside world), and we could think of the
> "objects" that it manipulates as a set of "resources" (but that would be
> problematic because all those database records or whatever are not exposed
> to the outside world).  We called this a "turtle" in Rennes (partly in
> reference to the classic anecdote from Steven Hawking
> http://members.tripod.com/TheoLarch/turtle.html
> and partly in reference to Clay Shirky's application of this joke to the
> services world
> http://webservices.xml.com/pub/a/ws/2001/10/03/webservices.html). The
> about "turtles" is that you only deal with the hard shell that
> them, and you don't care how many other "turtles" they are stacked on.
> References to Dr. Seuss
> -1/ref=sr_8_1/002-5339658-0637608?v=glance&s=books&n=507846 were
> :-)
> Sitting on top of the "turtle" is an agent that understands its internal
> semantics, APIs, data formats, etc. and can implement specific web
> interfaces.  This is (I think) what the targetResource URI identifies.
> also (more or less, and in my opinion) what we call "service" in the
> public working draft.  This agent is the thing that has a unique identity
> far as a Web service requester is concerned, and the thing with semantics,
> management interface, etc. as far as other aspects of the WSA architecture
> is concerned.  In the examples, this would be the SOAP interface that the
> ERP vendor offers, or the external view of the BPEL process.
> The rest of the stack is pretty much as WSDL envisions -- working top
> there's a  service which is a collection of endpoints, each of which has
> or more bindings, and each binding describes a messaging protocol that
> describes how a service requester communicates with a service provider
> "agent") to perform a specific operation.
> So, I think that addressed Ugo's concern: the agent *is* the WSDL
> targetResource, and had a URI.  All sorts of resources *could* exist
> the agent, but all a Web service requester sees is the agent.  To address
> Mark's concern, the problem this attempts to solve is basically service
> aggregation (different WSDL services may refer to the same targetResource)
> and discovery (you may want to locate a service by the properties of the
> actual provided "resource" (e.g., "a printer in my building") rather than
> the properties of the interface description.  Furthermore, "there will be
> services that operate on resources whose identity is only determined at
> runtime" is true, but it is the "target resource agent"'s job to figure
> out, out of sight of the service requester.
> Does this make any sense?
Received on Wednesday, 21 May 2003 21:28:57 UTC

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