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RE: On WSDL attributes

From: David Orchard <dorchard@bea.com>
Date: Wed, 10 Sep 2003 12:23:53 -0700
To: "'Jeffrey Schlimmer'" <jeffsch@windows.microsoft.com>, "'Savas Parastatidis'" <Savas.Parastatidis@newcastle.ac.uk>, "'WS Description List'" <www-ws-desc@w3.org>
Message-ID: <01fb01c377d1$12d428b0$900ba8c0@beasys.com>
+1.  Any extra constraints should be layered on top via extensibility.

Cheers,
Davce

> -----Original Message-----
> From: www-ws-desc-request@w3.org [mailto:www-ws-desc-request@w3.org]On
> Behalf Of Jeffrey Schlimmer
> Sent: Wednesday, September 10, 2003 12:20 PM
> To: Savas Parastatidis; WS Description List
> Subject: RE: On WSDL attributes
> 
> 
> 
> Savas, we agree. General Web services do not need a first-class notion
> of persistent state associated with a service.
>  
> Adding functionality to the Web service model necessarily implies
> additional constraints on underlying implementations. To facilitate
> cross-platform interoperability, we must be careful to minimize the
> architectural constraints on implementations. The current
> message-oriented definition of Web services appears to be an excellent
> tradeoff between function and minimal architectural commitment.
> 
> There are communities who wish to associate state with service
> instances; our WG should ensure that they can do so through
> extensibility.
> 
> --Jeff
> 
> > -----Original Message-----
> > From: www-ws-desc-request@w3.org [mailto:www-ws-desc-request@w3.org]
> On
> > Behalf Of Savas Parastatidis
> > Sent: Tuesday, September 09, 2003 4:44 AM
> > To: WS Description List
> > Subject: On WSDL attributes
> > 
> > 
> > All,
> > 
> > Here are some thoughts by Jim Webber and myself on the 
> introduction of
> > attributes in WSDL...
> > 
> > 
> > The proposal on the introduction of attributes in the WSDL
> specification
> > has come a long way due to the work that the relevant Task Force has
> > produced. The most recent update to the proposal is, we believe,
> closer
> > to the WSDL way of describing message exchanges. However, it is so
> close
> > that we believe attributes are not necessary for WSDL.
> > 
> > 1. Attributes represent a concept that it is not part of the Web
> > Services Architecture. Nowhere in the WSA document, to our 
> knowledge,
> is
> > it suggested that a Web Service has attributes. Web 
> Services send and
> > receive messages. They do not have operations, functions, 
> methods, or
> > attributes as it is the case with object-based component 
> models. WSDL
> is
> > used to describe messages that can be sent and received. 
> The notion of
> > an "attribute" attempts to add a characteristic to Web Services that
> > simply does not exist.
> > 
> > 2. The current version of the proposal defines particular message
> > exchange patterns. Since there is already work being carried out in
> this
> > area, we feel that there is no need for the introduction of 
> attributes
> > in WSDL. For instance, the notion of a solicit-response MEP is
> somewhat
> > analogous to "getting" an attribute, while a request-only MEP is
> > analogous to "setting" an attribute. Given these abilities which are
> > already an accepted part of WSDL, this undermines the need 
> for "read",
> > "read-write", and "write" qualifiers for attributes.
> > 
> > To summarise: We believe that attributes are a fundamental 
> property of
> > object-based systems, and do not have a corresponding use in SOA. We
> are
> > supported by WSA in this thinking. Furthermore, we believe that the
> > benefits of an attribute style interaction in terms of being able to
> > "set" or "get" structured XML data from a Web service is already
> > supported with WSDL operations.
> > 
> > While we think that the work of the ATF is correct in 
> itself, we would
> > oppose the inclusion of such work into WSDL, and would instead
> > anticipate that it would form part of some other specification which
> > leverages WSDL extensibility. Those communities which have a
> > demonstrated need to deploy Web services in a distributed 
> object-like
> > scenario (e.g. Grid), can then utilise the separate attribute
> > specification to support their needs, without adding 
> non-WSA features
> to
> > WSDL.
> > 
> > Regards,
> > Jim Webber
> > Savas Parastatidis
> > 
> 
> 
> 


Received on Wednesday, 10 September 2003 15:27:05 GMT

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