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RE: Web Service Description and stateful services

From: Savas Parastatidis <Savas.Parastatidis@newcastle.ac.uk>
Date: Tue, 20 May 2003 12:52:42 +0100
Message-ID: <BC28A9E979C56C44BCBC2DED313A447001C0C0BA@bond.ncl.ac.uk>
To: "Christopher B Ferris" <chrisfer@us.ibm.com>, "Sergio Andreozzi" <sergio.andreozzi@cnaf.infn.it>
Cc: <www-ws-arch@w3.org>, "Steve Graham" <sggraham@us.ibm.com>

Steve Graham (cc'd) is representing GGF in the WSD WG. It is my
understanding that he has already been given the task of coming up with
a proposal for the WG's next F2F.

I have my personal thoughts on how state should be managed and exposed
that is not aligned with the current view in the Grid community but this
is not the place to discuss them :-)

.savas.

> -----Original Message-----
> From: Christopher B Ferris [mailto:chrisfer@us.ibm.com]
> Sent: Tuesday, May 20, 2003 12:43 PM
> To: Sergio Andreozzi
> Cc: www-ws-arch@w3.org
> 
> 
> Sergio Andreozzi wrote on 05/20/2003 07:03:16 AM:
> 
> >
> > Dear WS-ARCH group members,
> >
> > the Web Services description is currently defined in the latest Web
> > Service Architecture document (1.5.3) as:
> >
> > "The service description is a machine processable specification of
the
> > message formats, datatypes and protocols that should be used between
the
> 
> > requester agent and the provider agent. It also specifies the
network
> > location of the provider agent, and may provide some information
about
> > the message exchange pattern that is expected"
> >
> > In the research community, I've seen some attempt at representing
the
> > service state by using WSDL extensions, i.e. by extending the web
> > service description with attributes that carry the information
related
> > to the current state of a service. This means that, for each service
> > instance, a WSDL document should be created.
> 
> Yes. And, I assume by "research community" that you refer to the
> work on the GRID? Or is this some other similar work?
> 
> >
> > I would like to receive your point of view on the following issue.
From
> > the definition you give, I understand that the service state is a
> > concept more related to the service representation (def. 2.2.29),
while
> > the service description (def. 2.2.32) should describe service
interface
> > and semantics.
> >
> > Extending a WSDL document with service representation related data
is
> > somewhat merging service description with service representation.
This
> > solution might be handy when you want, for instance, advertise the
> > quality related attributes in order to make a QoS based discovery.
> 
> Agreed, it is blurring the distinction between the two concepts, but
as
> you
> point out, it can indeed be useful for such things as QoS-based
discovery.
> Of course, you could also make use of the Notification service and
> have instances advertise their service data in that manner and still
> be able to effect QoS-based discovery (assuming that some discovery
> agent is facilitating the job by subscribing to servicedata, etc.)
> 
> >
> >  From a Web Service Architecture point of view, how do you deal with
> > this issue and the above solution?
> 
> Well, this really should be discussed ay length in the WSD WG as part
> of the process of incorporating such an extension in WSDL1.2.
> 
> I think you raise an interesting point, and that you should do so in
the
> context of WSD WG to call it to their attention.
> 
> Cheers,
> 
> Chris
> 
Received on Tuesday, 20 May 2003 07:52:53 GMT

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