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Re: question about "Semantic Annotations for WSDL"

From: David Martin <martin@AI.SRI.COM>
Date: Thu, 02 Mar 2006 11:46:35 -0800
Message-ID: <44074B9B.50103@ai.sri.com>
To: "Shi, Xuan" <xshi@geo.wvu.edu>
CC: "'public-sws-ig@w3c.org '" <public-sws-ig@w3c.org>

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.

Hello Xuan -

Evidently you either didn't read or didn't understand what I posted.
I think you have some good ideas, but at the same time I don't think
your comments are really related to the question and points that I
raised.  (Of course they are related at a high level but definitely
not directly related.)  Frankly, I find it a bit frustrating.  I
started this thread to invite some discussion about a question that
*I* had in mind - not to provide another opportunity for you to get
out your message.

Guess what?  In this case my posting was actually quite sympathetic to
your point of view!  Here's a brief paraphrase:

David: This business of annotating WSDL, with references to semantics
that are expressed in a separate formalism, seems to have at least one
serious weakness ... I'm worried that the approach won't be useful over
the long term.

Xuan: What??? You *still* want to talk about adding semantics to
WSDL??? That's rubbish, and here's why ...

Hello ... In this posting I was raising a *criticism* of trying to add 
semantic annotations to WSDL (at least of one particular approach) - not 
*advocating* it.

Don't get me wrong.  You have every right to express your opinions on
the list and it's great to do so, especially if you feel passionately
that things can be done a better way.  But I would like to suggest
that you can make a greater contribution if, when a new thread is
started, you make every effort to understand the points and respond
more directly to them.


> 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 Thursday, 2 March 2006 19:46:54 UTC

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