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RE: question about "Semantic Annotations for WSDL"

From: Shi, Xuan <xshi@GEO.WVU.edu>
Date: Mon, 27 Feb 2006 22:07:13 -0500
Message-ID: <D81F456794C18B4DA3E2ABC47DBBEEF2094F78@www.geo.wvu.edu>
To: "'David Martin '" <martin@AI.SRI.COM>, "'public-sws-ig@w3c.org '" <public-sws-ig@w3c.org>
Cc: "Shi, Xuan" <xshi@GEO.WVU.edu>

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 Tuesday, 28 February 2006 03:07:37 UTC

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