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RE: Web Service Description and stateful services

From: Ugo Corda <UCorda@SeeBeyond.com>
Date: Tue, 20 May 2003 09:47:43 -0700
Message-ID: <EDDE2977F3D216428E903370E3EBDDC90811B9@MAIL01.stc.com>
To: "Savas Parastatidis" <Savas.Parastatidis@newcastle.ac.uk>, <www-ws-arch@w3.org>

I noticed that OGSI gave a presentation during the recent WSD F2F, and a debate followed. 
See the minutes at http://lists.w3.org/Archives/Public/www-ws-desc/2003May/0051.html, section "OGSI ServiceData - Steve Graham" (also has a pointer to the OGSI presentation slides).


> -----Original Message-----
> From: Savas Parastatidis [mailto:Savas.Parastatidis@newcastle.ac.uk]
> Sent: Tuesday, May 20, 2003 7:15 AM
> To: Cutler, Roger (RogerCutler)
> Cc: www-ws-arch@w3.org
> Subject: RE: Web Service Description and stateful services
> Here's a (very) brief description...
> The Open Grid Services Architecture (OGSA) specifies the services that
> an OGSA-compliant platform should support. The specifications of those
> services are defined by various GGF working groups (work still in
> progress). However, all the services MUST adhere to the Open Grid
> Services Infrastructure (OGSI) specification.
> OGSI defines the notion of a Grid Service Instance, which is 
> a stateful
> web service with lifetime related characteristics. A factory 
> pattern is
> employed to create service instances.
> There is a Grid Service Description document which defines 
> the interface
> of Grid Service Instances and it is written in WSDL, with two
> non-conformant extensions:
> 1. portType inheritance ("portType" has been renamed to "interface" in
> WSDL 1.2 and the "extends" attribute has been included). This is not a
> problem when we move to WSDL 1.2.
> 2. Service Data Elements (SDE)
> SDEs are used to declare JavaBeans-like properties to services or
> C++/Java like class/instance data members.
> The "serviceData" element can appear in a portType and defines the
> structure of exposed state. It has most of the attributes of 
> xsd:element
> with some additions. The way that "serviceData" is included 
> in the WSDL
> does not conform to WSDL 1.1 or 1.2. Furthermore, the way the
> "serviceData" element has been defined does not conform to the
> XML-Schema. I have already submitted a proposal that, if 
> accepted, will
> at least solve the non-conformance issues. 
> Effectively it is a way to declare properties for services. The spec
> does not associate these properties with messages. Instead, specific
> operations are made available from the GridService portType (the one
> that all Grid Service Instances must inherit) that allow 
> get/set access
> to the SDEs by using their names as arguments.
> Although SDEs can be declared as part of a portType, the spec 
> allows the
> introduction of new SDEs at runtime. "Introspection" operations are
> defined in the GridService portType. Also, consumers can subscribe to
> SDEs to receive notifications.
> The OGSI working group would like to see SDEs as part of WSDL.
> I hope the above give a flavour.
> I believe that the entire OGSI architecture is too object-oriented for
> my liking. I have many issues with the approach, as I suggested in a
> previous message, that I will bring to the OGSI working group. This
> mailing list is not the place.
> Regards,
> --
> Dr. Savas Parastatidis 
> Chief Software Architect, North-East Regional e-Science Centre 
> School of Computing Science, University of Newcastle upon Tyne, UK 
> http://savas.parastatidis.name
> > -----Original Message-----
> > From: Cutler, Roger (RogerCutler)
> [mailto:RogerCutler@chevrontexaco.com]
> > Sent: Tuesday, May 20, 2003 2:51 PM
> > To: David Orchard; Christopher B Ferris; Savas Parastatidis
> > Cc: www-ws-arch@w3.org
> > 
> > 
> > I'd still like to hear specifically what these people are doing and,
> if
> > possible, what motivated them to put it in this place.
Received on Tuesday, 20 May 2003 12:47:51 UTC

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