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Review of WSDL 2.0 - RDF Mapping

From: Booth, David (HP Software - Boston) <dbooth@hp.com>
Date: Thu, 22 Dec 2005 15:46:20 -0500
Message-ID: <A5EEF5A4F0F0FD4DBA33093A0B07559008911DDE@tayexc18.americas.cpqcorp.net>
To: <public-ws-desc-comments@w3.org>
Cc: "Jacek Kopecky" <jacek.kopecky@deri.org>, "Bijan Parsia" <bparsia@isr.umd.edu>

Document reviewed: "Web Services Description Language (WSDL) Version
2.0: RDF Mapping"

The document thus far only describes the ontology that will be used for
the resulting RDF.  The mapping itself is still marked as a "to do", so
I cannot comment on that.  I wonder: Will the mapping be defined in
XSLT?  That would be really convenient if it is feasible.  And if not, I
am curious to know why not, since the need to map from the XML world to
the RDF world is likely to be increasingly common.

The document notes that the customer base for this work product is
unclear.  However, even apart from its value for direct use, I view this
work as a valuable exercise in bridging from XML to RDF.  Lessons
learned will be helpful to others.

The design of the ontology corresponds almost directly to the design of
the WSDL 2.0 component model, which makes it easy to understand.  The
deviations also seem to be straightforward and sensible.  In general,
the document is written quite clearly.

The document clearly says that the ontology is less constraining than
the WSDL 2.0 specfication.  I wonder: would it be feasible to itemize
the constraints that are present in the specification but not enforced
by the ontology?  To what extent would this be feasible?  If it is
feasible I think it would provide greater insight into the ontology. 

Section 1. Introduction: 
Good motivation.  If the creation of WSDL2.0-->RDF mapping helped to
expose unnoticed issues in the WSDL 2.0 definition, that would be good
to mention also.

Section 2.2 Handling Features, Properties and Generic Extensions: 
Good overview of WSDL 2.0 extensibility.

Section 3. Differences from the WSDL Component Model:
I found myself getting confused about whether a paragraph was discussing
the RDF that results from mapping a legal WSDL document, versus
arbitrary RDF that might be written using the ontology and thus may not
correspond to any legal WSDL document.  The document as a whole is about
the mapping from legal WSDL documents, and thus as a reader I kept
expecting to be reading about the RDF that results from mapping a legal
WSDL document. 

Section 3.1 Component naming:
Re: "The original names and namespaces are not explicitly modeled in the
RDF representation"
I found myself wondering which namespace this section was discussing,
but I think it is referring to the wsdl:targetNamespace.  It would be
good to clarify.

I notice that in section 3.1 the ontology runs into the issue of the
dependency between the meaning of a hash URI and the mime type of the
content that is returned from that URI, and thus the need to dereference
the URI to determine the mime type.  This is exactly the kind of problem
I describe in my discussion of how URIs/IRIs should be minted:

Section 3.2 Documents, imports and includes:
I don't understand this sentence: "Strictly speaking, interfaces don't
need to belong to any Description, and interface operations don't
actually need to belong to any interface in the RDF representation.".
Is it referring to your ontology in general or to your mapping?  I
thought a wsdl:interface MUST belong to a wsdl:description, so I would
think that in any RDF resulting from applying the mapping that you
describe, each interface *would* belong to a Description and each
interface operation *would* belong to an interface.  In retrospect, it
looks like that sentence is referring to the ontology in general.  This
is an example of the confusion I mentioned under section 3.1 above.

I don't understand the implications of section 3.2.

Appendix A: the owl ontology source:
I notice that a lot of properties have rdfs:range defined, but not
rdfs:domain.  I assume this is because these properties could be applied
to more than one class.  Would it make sense to create some superclasses
for these, so that the rdfs:domains can be specified?


s/and that it doesn't mandate/and it doesn't mandate/

s/should also provide URIs/should also provide IRIs/


This is a key conceptual point:
a Z based validator will complain that that representation is ill formed
(given the WSDL specification). An OWL reasoner encountering it will,
all other things being equal, conclude that there *is* such a property,
albeit unknown.
The last sentence may be confusing to readers who are not so familiar
with the open world assumption.  Perhaps the following might be slightly
An OWL reasoner encountering it will, all other things being equal,
conclude that there *is* such a property, even though the reasoner has
not yet seen it.


s/WSDL spec prescribes/WSDL specification prescribes/

s/RD representation/RDF representation/

s/may extend other interface/may extend other interfaces/

s/The one notable exception are/The notable exceptions are/

David Booth, Ph.D.
HP Software
Phone: +1 617 629 8881
Received on Thursday, 22 December 2005 20:47:19 UTC

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