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RE: Web Service Description and stateful services - (on the 'ww w-ws@w3.org' list) Debating on a) Stateful Web Service Instances b) St ateful Interaction - OGSI

From: Champion, Mike <Mike.Champion@SoftwareAG-USA.com>
Date: Fri, 20 Jun 2003 05:53:40 -0600
Message-ID: <9A4FC925410C024792B85198DF1E97E405F292D5@usmsg03.sagus.com>
To: www-ws-arch@w3.org

 

> 
> -----Original Message-----
> From: marco [mailto:events@oxfordsociety.org] 
> Sent: Friday, June 20, 2003 5:36 AM
> To: www-ws-arch@w3.org
> 
> 

> In particular, in relation to OGSI spec: 
> Is it appropriate for the web service community to support a) 
> or is that a wrong OO mindset that we should abandon?

Interesting question, but I don't know that this is related to the question
of statefulness.  
> 
> Web Service composition languages have already some notion of 
> a) and b) Here we are talking of a) and b) in relation to a 
> single non-composed web services.

FWIW, the W3C Choreography effort was founded to describe "long running
stateful interactions using Web services", so if we're talking about
multiple invocations of single non-composed Web services that change some
shared state, we're talking about "choreography."

> 
> WSDL and SOAP don't support:
> a) The concept of stateful service instance
> b) Stateful interaction


I'm a bit unclear how a "single non-composed web service" could *logically*
imply a shared state.  SOAP and WSDL describe a single interaction between a
consumer and provider, any understanding of the state this puts the larger
system in must be in a higher level description. Obviously people *do* use
SOAP in multipart, stateful interactions, but I think the understanding of
the state semantics is passed around "out of band".  This is why BPEL and
similar technologies have gotten so much attention over the last year!

> -  Object passing, neither by value nor by reference
> 
> I use the term "Stateful Web Service Instance" with a meaning 
> compatible with the following: "Grid services can maintain 
> internal state for the lifetime of the service. The existence 
> of state distinguishes one instance of a service from another 
> that provides the same interface. We use the term Grid 
> service instance to refer to a particular instantiation of a 
> Grid service. " [6.1 The OGSA Service Model] In this meaning, 
> the relation between a web service and its stateful service 
> instances vaguely resemble the one of a class and its objects.
> If Stateful Service Instances are supported, issues such as 
> lifetime management and remote instance references must be 
> taken into account. In this meaning, "Stateful Web Service 
> Instance" are today neither pervasive nor standard.

Right, again see the interest in "choreography", "business process
description," etc. recently.  It might be interesting to make sure that the
OASIS BPEL folks and the W3C Choreography folks have your useage scenario in
mind.

> 
> Would it be appropriate for SOAP/WSDL to support a) and b) ?
> Is it appropriate for the web service community to support a)
> or is that a wrong OO mindset that we should abandon? 
 I don't quite follow the a) and b) distinctions, but I'm pretty sure that
the basic semantics of SOAP and WSDL are more or less fixed, and what you
are asking for belongs in a Choreography layer above them.
Received on Friday, 20 June 2003 07:54:03 GMT

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