Re: FWD [Work in Progress on Semantics for Web Services (Advance Notice)]

Greetings,

It has certainly been the experience of OGC work in Geospatial Web  
services that neither WSDL nor OWL-S (nor OGC Capabiliities) is yet a  
full and actionable description of services by itself. WSDL is all  
about syntax and says nothing explicitly about either semantics or  
content coupling. OWL-S still (at least from my perspective) lacks  
the ability to describe content coupling. Yet I do appreciate the  
approach of OWL-S not to throw away the useful contributions of WSDL  
to Web services syntax description in the process (so to speak) of  
going beyond it.

This does, however, leave me with a sneaking suspicion that no  
service description approach is perfect.  An important adjunct to any  
such scheme will be an explicit description of its knowledge  
preconditions – in what knowledge community will the descriptions be  
useful and understandable. So far we've been better at serving  
"ourselves" than at serving "others" whether in the GIS community or  
elsewhere.

Josh Lieberman

Joshua Lieberman, Ph.D.
Principal, Traverse Technologies Inc.
mailto:jlieberman@traversetechnologies.com
tel +1 (617) 395-7766
fax +1 (775) 514-6621

On Sep 1, 2005, at 2:44 PM, David Martin wrote:

>
> Hi Xuan -
>
> Thanks for your comments.  You make some good points about OWL-S  
> and other SWS approaches such as WSMO.  But it appears to me that  
> you are giving an inaccurate picture of what OWL-S is about, so I  
> would like to provide a clarification.  Your comments seem to be  
> based on the assumption that OWL-S is only meant to be used in a  
> "backward-engineering" style; that is, only meant to be used to  
> annotate pre-existing WSDL services, which were designed  
> independently from Semantic Web approaches.
>
> Here I only want to point out that OWL-S was not primarily  
> conceived for use in that "backward-engineering" style.  As Alois  
> Reitbauer has also pointed out in a previous message, it is  
> possible to employ Semantic Web approaches in a forward-engineering  
> methodology; that is, incorporating ontology-based semantics from  
> the beginning in the design process.  A number of researchers have  
> been working on this way of doing things, and tying it in with  
> widely used methods such as those based on UML. Furthermore, please  
> note that WSDL-specified Web services are not mandated to use XML  
> Schema to describe their inputs and outputs.  WSDL has  
> extensibility mechnisms that allow for other "typing" mechanisms.  
> Thus it is possible to imagine Web services that are "native  
> speakers" of OWL (their inputs and outputs are exchanged using one  
> of OWL's serialization syntaxes), which would largely address the  
> gap that you describe between a WSDL and an OWL-S specification.
>
> I hasten to add that no such services exist today, and furthermore  
> there are some unresolved difficulties.  (These have to do with the  
> fact that OWL instances can be serialized in so many different  
> ways, and there can be ambiguity regarding how much content needs  
> to be carried to adequately characterize an OWL instance.)   
> However, there has been a good deal of discussion about these  
> difficulties, and I believe they can be addressed.  Presumably this  
> might be a topic of concern if any SWS standardization or pre- 
> standardization activities materialize at W3C.
>
> Finally I would like to add that there is no basis for your  
> characterization that SWS is "big business".  There is a great deal  
> of research interest in these technologies because the promise is  
> so great, but that's not at all the same as saying that it is "big  
> business". (For instance, I do not know of any companies that are  
> trying to ensure profits by trying to control the direction of SWS  
> standardization activities.)  I am certain that Carine is only  
> trying to make progress possible by considering some activities  
> that would promote greater collaboration between those who are  
> working on WS and those who are working on SWS, so that (among  
> other things) we can make further progress towards addressing  
> issues such as those that you raise.
>
> Regards,
> David Martin
>
> Shi, Xuan wrote:
>
>
>> Dear Dr. Bournez:
>> I joined this working group and mailing list but cannot add my  
>> comments into
>> the archive. Maybe my opinion is not welcome but I hope more and  
>> more people
>> can understand what' wrong for those research approaches on  
>> semantic Web
>> services research when they are used in real world development. I  
>> think I
>> contacted you and many other W3C staffs, directors and writers of  
>> OWL-S,
>> WSMO, WSDL-S. I hope people in this working group will not keep  
>> silence on
>> those known problems.
>> In my opinion, the mechanism of OWL-S looks like a backward- 
>> engineering
>> process. Since WSDL is the outcome of OOP, then what OWL-S can do  
>> is only
>> restore the object hierarchy and relationship in the development  
>> process of
>> OOP. In this way, every object used in the Web services can be  
>> associated
>> with others under such framework but OWL-S cannot describe the  
>> meaning of
>> the objects used in the OOP. WSDL-S makes things worse since it  
>> only “adds” semantics onto certain
>> objects while remains the others undefined, that is to say, given the
>> example of Address Finder Web Service (URL can be accessed at:
>> http://arcweb.esri.com/services/v2/AddressFinder.wsdl ), WSDL-S  
>> would only
>> add semantics onto such WSDL elements like street, intersection,  
>> city,
>> state_prov, zone, country, user name, password, but ignore the other
>> elements such LocationInfo, ArrayOfLocation, Location[],  
>> description1,
>> description2, addressFinderOptions, token, matchType, etc. just  
>> because they
>> are not meaningful. Thus the whole WSDL file will be a mess for  
>> requesters
>> to understand and use. WSMO creates a conceptual model to describe  
>> the meaning of the service and
>> probably can be a useful approach to develop semantic Web services.
>> Unfortunately, WSMO by now has to “ground” to WSDL to connect both  
>> systems
>> together and to derive the service semantics. If WSDL is NOT the  
>> appropriate
>> source from which to derive data and service semantics, WSMO just  
>> associates
>> with a wrong object and thus cannot get the correct result. Thus  
>> if there is
>> no way to “ground” to WSDL, WSMO is useless as a stand-alone  
>> framework.
>> In conclusion, the source of the problem in their research on  
>> semantic Web
>> services is that researchers just used some simple business  
>> transaction
>> models and then the whole process is simplified. That is to say,  
>> all WSDL
>> elements used in such simple models are intuitive and self- 
>> understandable.
>> However, given the example in Address Finder Web Service, most of  
>> WSDL
>> elements are meaningless, redundant, and irrelevant to the users  
>> to set up a
>> direct relation between the input variables and output results.  
>> When we try
>> to use such real-life cases to test those mechanisms, then we can  
>> find the
>> true problems. I tried to CMU's WSDL2OWLS tool to convert the WSDL  
>> file of
>> Address Finder Web Service into OWL-S, the result is almost  
>> meaningless and
>> users still cannot understand the meaning of the service.  
>> Unfortunately,
>> CMU's Web site for testing their tool is down and maybe they just  
>> knew OWL-S
>> approach cannot solve the problem.
>> What's the semantics for Address Finder Web Service? The direct  
>> and explicit
>> meaning of this Web service is: if the user can provide user name,  
>> password,
>> and address information on street, city, state (or province), zip/ 
>> post code,
>> then the service will return the location of the input address.
>> I suggest that researchers should give up dealing with those  
>> simple business
>> transaction models. I know SWS now is a big "business" but please  
>> test your
>> approaches and see if your approach can describe the meaning of  
>> "Address
>> Finder Web Service". If it fails, you have to consider what's  
>> wrong and
>> reformat your approach. Don't tell people that your approach can  
>> work find
>> with credit card transaction, buy book, ticket, purchase order,  
>> etc. etc....
>> They are just meaningless in the real world.
>> Any comments and suggestions will be greatly appreciated. I hope  
>> W3C and SWS
>> committee members will not keep silence any more to this challenge  
>> since
>> many of them already knew the content of this message for a rather  
>> long
>> time. I look forward to hearing from you.
>> Best wishes,
>> Xuan
>> -----Original Message-----
>> From: Carine Bournez
>> To: Battle, Steven Andrew
>> Cc: public-sws-ig@w3.org
>> Sent: 9/1/05 6:11 AM
>> Subject: Re: FWD [Work in Progress on Semantics for Web Services  
>> (Advance
>> Notice)]
>> On Thu, Sep 01, 2005 at 10:50:47AM +0100, Battle, Steven Andrew  
>> wrote:
>>
>>> Carine,
>>> Can you shed any light on the decision here to establish a  
>>> charter for
>>>
>> a
>>
>>> new working group rather than - or perhaps in addition to - a  
>>> lighter
>>> weight incubator activity. The attendee poll at the FSWS workshop
>>>
>> found
>>
>>> little enthusiasm for such a working group. What caused this  
>>> shift in
>>> opinion at the W3C?
>>> Steve.
>>>
>> Steve, all,
>> This "Advance Notice" is precisely aiming at gathering feedback about
>> the
>> way to go. W3C Members are aware of lightweight process and should  
>> react
>> on member-ws@w3.org about this process.
>> Thank you for raising this point.
>>
>
>