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schemaMapping issues breakdown (issue 6)

From: Jacek Kopecky <jacek.kopecky@deri.org>
Date: Tue, 23 May 2006 16:51:28 +0100
To: SAWSDL public list <public-ws-semann@w3.org>
Message-Id: <1148399488.24863.31.camel@localhost>

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. Therefore 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".)

Hope it makes sense,

Jacek Kopecky

[1] http://www.w3.org/2002/ws/sawsdl/issues/#x6
Received on Tuesday, 23 May 2006 15:58:15 GMT

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