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RE: question about "Semantic Annotations for WSDL"

From: Jacek Kopecky <jacek.kopecky@deri.org>
Date: Mon, 13 Mar 2006 15:52:17 +0100
To: "Shi, Xuan" <xshi@GEO.WVU.edu>
Cc: 'David Martin ' <martin@AI.SRI.COM>, "'public-sws-ig@w3c.org '" <public-sws-ig@w3c.org>
Message-Id: <1142261537.17177.86.camel@localhost>


I disagree with your point that WSDL has NO relation to the semantics of
the service. If the service does something (like addition), the WSDL
will likely have at least one operation that accepts a set of numbers
(in some way) and produces one number. Granted, an addition operation
modeled in multiple environments will be syntactically different, even
very different. 

But I believe that you must acknowledge that the WSDL is built from the
semantics of the service. Therefore, provided we can describe the
semantics and give a URI to them, we can also point from WSDL to that
URI using modelReference (WSDL-S construct), and in an ideal situation
two different WSDLs for addition operation will both point to the same
addition operation semantic description, and an automated tool can
assume that the operations are functionally interchangeable.

Resolving the syntactical differences between the two WSDLs is done by
what we call grounding from the semantic level to the XML level in WSDL,
and it will not be trivial, of course, but it's being worked on and I'm
not aware of any show-stopper problems. With proper grounding, it should
be possible for one agent to be able to invoke either of the addition
services (or any newly discovered ones) automatically if it wants to
perform addition.

Do you still think that WSDL annotations pointing to semantics cannot be
useful? If not, do you have any alternatives?

Best regards,


On Mon, 2006-02-27 at 22:07 -0500, Shi, Xuan wrote:
> Dear Dr. Martin,
> If you and this group would like to discuss the semantics of WSDL other than
> the semantics of Web service, then you can ignore the following lines
> because I will demonstrate again that the meaning of the element/component
> within WSDL interface document is NOT the meaning of Web service.
> Given a simple example, a Web service provides a function of addition
> calculation. How many different ways can we try to build such a function? I
> can give a list of functional interfaces as I discussed before, and you may
> wish to add more:
> Function addition (integer X, integer Y):integer Z
> Function addition (double X, double Y):double Z
> Function addition (integer X[2]):integer Z
> Function addition (double X[2]):double Z
> Function addition (number X, number Y):number Z
> Function addition (object O):integer Z (O has properties X, Y, or O has
> X[2])
> Function addition (string req):string resp (by SRR document)
> ... ...
> What's the meaning of this service and function? The meaning of service and
> function has any relationship with WSDL interface, process, precondition,
> effect, etc.? 
> As a common sense, the meaning of ALL such Web services is the same: it will
> add two numbers and return the result back to requester. When you add
> semantic annotations into WSDL, can you describe the meaning of this Web
> service?
> Let's change the function name into subtraction, multiplication, and/or
> division. Then all elements in the WSDL document are the same except the
> name of the function. Should you want to clarify that the X variables used
> in every different function are all the same or not? It seems you still care
> more about the name of the element inside a WSDL document, not the meaning
> of Web service.
> Let's design another Web service that will perform mixed calculation by
> using the above four Web services. While we can design the interface of such
> a service and function in many many different ways, the meaning of this Web
> service is: if requesters send a number sentence to provider, the provider
> will send back the result of the mixed calculation.
> Do you think the provider should tell requester that the provider will
> aggregate one or more Web services (addition, subtraction, multiplication,
> division) in the OWL-S approach, or how the provider will mediate the four
> Web services in WSMO approach, to generate the result? 
> In conclusion, the meaning of Web services has NO relation with both of the
> WSDL interface and the aggregation/mediation process. Then I don't think
> it's worthy to add semantic annotations for WSDL since such activity cannot
> lead to the goal of semantic Web services.
> Best wishes,
> Xuan
> -----Original Message-----
> From: David Martin
> To: public-sws-ig@w3c.org
> Sent: 2/27/06 6:59 PM
> Subject: question about "Semantic Annotations for WSDL"
> Here is an important question about the proposed "Semantic Annotations
> for WSDL" working group, about which I'd love to see some discussion.
> The current draft charter is here:
>    http://www.w3.org/2005/10/sa-ws-charter.html
> Question:
>      Does the envisioned approach provide a foundation that will be
>      useful in working with, or evolving to, a more comprehensive
>      framework, or simply a detour that will ultimately fall out of use
>      (if Web service semantics become important)?
> What's behind this question is the observation that, from a
> WSDL-centric perspective, the semantic artifacts referenced by a WSDL
> spec will be disconnected.  That is, from the point of view of a WSDL
> tool, they won't exist in the same declarative scope. (Indeed, in this
> approach there is *no* notion of declarative scope for the semantic
> artifacts, from the WSDL perspective.)
> One way to illustrate this concern is simply by observing that
> preconditions and effects associated with services will frequently
> have variables in common.  To have a coherent representational scheme,
> it is of fundamental importance to spell out the relationship between
> variable X mentioned in a precondition and variable X mentioned in an
> effect expression.  From the perspective of a WSDL tool, there won't
> be any basis for establishing or working with such a relationship.  So 
> the concern here is that a WSDL tool ultimately won't be able to do much
> with the semantic declarations that are referenced.
> Of course, the semantic framework underlying those declarations may
> provide the basis that ties the semantic declarations together, and a
> WSDL tool could build in some understanding about one or more of the
> semantic frameworks that may be used in connection with WSDL.  But the
> point is that it's not a WSDL tool anymore - it's a WSDL tool plus a
> {UML or OWL-S or WSMO or SWSF or METEOR-S or ODESWS or ...} tool.  And
> as far as I can tell, there won't be any meaningful connection between
> the two tools.  The concern is that the proposed approach does not
> appear to provide any path by which such a meaningful connection might
> eventually be achieved.
> Cheers,
> David Martin
> SRI International
Received on Monday, 13 March 2006 14:52:24 UTC

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