RE: question about "Semantic Annotations for WSDL"

David,
I guess I put myself in the 'cup is half full' camp :)
See my comments inline..

Steve.
(Hewlett Packard)

> -----Original Message-----
> From: public-sws-ig-request@w3.org 
> [mailto:public-sws-ig-request@w3.org] On Behalf Of David Martin
> Sent: 28 February 2006 00:00
> To: public-sws-ig@w3c.org
> 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.)
>

Certainly, WSDL extensions don't exist in the document scope in any
well-defined way. This is why I don't consider the RDF mapping of WSDL
as an optional extra. Ultimately, semantic annotations should be added
to the same model as the RDF mapping, and this will put them on the same
footing.

In general, the meaning of extensions is unknown to the WSDL definition
and to any tools using that definition. One useful output of the
Semantic Annotation for WSDL WG would be to define the RDF mapping for
additional web-service semantics. I can imagine a future tool that would
model WSDL in terms of its RDF mapping, and would accept plug-ins
(implementing the SAW WG recommendations) that would support the
appropriate RDF mappings for semantic annotations.
 
> 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.

Scope is an interesting case because, of course, RDF really has only
'global' scope. But what is scope other than a lexical method of
identifying the right component. As long as we can still identify the
same component (variable) we can drop the lexical nesting. In a global
context we have to translate the lexical nesting into the URIs of the
variables themselves. In other words, the namespace of X should reflect
the process it belongs to. This allows the precondition and
postcondition of a process to refer to the same variable.

Again, no existing WSDL tool could possibly make any sense of the
extension, but I think one that supported semantic plug-ins could. In
other words it could produce the appropriate WSDL RDF mapping plus the
mapping defined for the extension, in this case an RDF expression of
pre/post-conditions.

> 
> 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.

For me, the backbone of this connection has got to be the RDF mapping
for WSDL.

> 
> Cheers,
> David Martin
> SRI International
> 
> 
>

Received on Thursday, 2 March 2006 20:13:54 UTC