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Re: schemaMapping issues breakdown (issue 6)

From: Rama Akkiraju <akkiraju@us.ibm.com>
Date: Tue, 30 May 2006 15:47:38 -0400
To: verma@cs.uga.edu
Cc: public-ws-semann@w3.org
Message-ID: <OF03937D45.156443EA-ON8525717E.006C58AE-8525717E.006CBB4B@us.ibm.com>

Kunal,

In the paper you referenced below, you talk about upcasting and
downcasting. Upcasting information is stored in the WSDL. Where would
downcasting information be stored? In the ontology? If so, how can we
burden an ontology to have pointers to elements in individual WSDLs? there
could many such WSDLs that may need downcasting. By this, may be you are
inferring that the concepts in the ontology have to updated to accommodate
enough information abou the terms used in WSDLs that are being matched. Is
this right? I am just guessing here. Can you please clarify where the
downcasting information be stored in your work?

Thank you.

Regards
Rama Akkiraju




                                                                           
             "Kunal Verma"                                                 
             <verma@cs.uga.edu                                             
             >                                                          To 
             Sent by:                  "Jacek Kopecky"                     
             public-ws-semann-         <jacek.kopecky@deri.org>,           
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             05/29/2006 01:45                                      Subject 
             PM                        Re: schemaMapping issues breakdown  
                                       (issue 6)                           
                                                                           
             Please respond to                                             
             verma@cs.uga.edu                                              
                                                                           
                                                                           
                                                                           




Hi all,

We worked on this issue when we were writing the WSDL-S spec. I agree with
Jacek's comments (especially option 1c). Comments are inline.

  Hi all,

  here's an attempt to break down what I think are the separate issues in

  clarifying schemaMapping (issue 6 [1]). This email is written with my
  chair hat off. 8-)

  I assume that schemaMapping attribute points to a document that


  specifies a transformation. It seems that there are two orthogonal sets

  of options that we need to consider. Wherever I use RDF below I mean any
  ontological data language (can be RDF, WSML or any such language of


  choice).

  1) The transformation is a) between an XML Schema on one side and an

  ontology on the other side (schema-level mapping) or b) between XML
  document conforming to the XML Schema on one side and RDF data that uses


  some ontology on the other side (data-level, runtime mapping).


  I believe option a) above is not useful because the XML Schema in WSDL
  is given and static, the transformation is as static, so the result is

  also static, and therefore it can be saved somewhere and pointed to
  using modelReference, as opposed to requiring the processor to take the
  schema, run the transformation, and arrive at the same result every
  time.

  herefore I assume 1b for the formulation and discussion of the



  following aspect:

  2) The transformation goes a) from XML to RDF, b) from RDF to XML, or
  c) both ways.

  Since I dismissed the option 1a above, schemaMapping cannot be used
  easily for discovery, instead it could be used when a service is



  discovered to work with the necessary semantic terms, and then the
  client that has instances of those terms wants to invoke the service so
  it has to transform between its semantic data and the XML that the


  service requires.


  I believe that we need to consider both directions because the service
  both consumes and produces XML messages, so messages for the service
  have to be created from semantic data, and messages from the service



  need to be parsed back into semantic data.

  Depending on whether SAWSDL wants to enable invocation or only discovery
  (and composition, which uses similar data), we may keep or drop
  schemaMapping, and if we keep it, we may need to talk about which



  directions of the mapping it should handle.

  The conclusion is that we have to decide whether we want schema-level
  mapping and whether we want data-level mapping, then what directions for
  the mapping(s) we want to handle. (I'd say "no, yes, both".)


I totally agree with this and I think that modelReference is sufficient if
providing a semantic match is the only concern. SchemaMapping becomes
important only during invocation, when the heterogeneties between the XML
data and the OWL instances have to be considered. Hence, I think that
option 1c) makes the most sense.


We have been working on the issue of providing mapping both ways. We call
it upcast (XML to ontological language) and downcast (ontological language
to XML).  I would like to share this paper that discusses some of the
heterogeneity that may arise and discusses as scenario that uses upcast and
downcast.

Meenakshi Nagarajan, Kunal Verma, Amit P. Sheth, John A. Miller, Jonathan
Lathem, Semantic Interoperability of Web Services - Challenges and
Experiences, Proceedings of the 4th IEEE Intl. Conference on Web Services,
Chicago, IL, September 2006 (to appear).
http://lsdis.cs.uga.edu/library/download/techRep2-15-06.pdf

Thanks,
Kunal

--
Kunal Verma,
LSDIS Lab, Dept. of Computer Science,
University of Georgia.
URI: http://lsdis.cs.uga.edu/~kunal
Received on Tuesday, 30 May 2006 19:47:48 GMT

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