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Semantics

From: Francis McCabe <fgm@fla.fujitsu.com>
Date: Fri, 12 Jul 2002 15:23:29 -0700
To: www-ws-arch@w3.org
Message-Id: <FE1C414E-95E5-11D6-9A73-000393A3327C@fla.fujitsu.com>
This goal addresses many problems in large scale systems as well as a 
number of business needs.

D-AG009 Semantics
  The web services architecture must support the capability for an entity 
to automatically discover a service and to automatically evaluate 
whether it is appropriate for its requirements.

Rationale:

  Enabling an entity to automatically locate and choose a service does 
not mean that people are not involved, nor does it mean that this must 
always involve some kind of late binding. However, discovering and 
evaluating are key aspects of the marketplace: without the ability to 
discover new suppliers and customers it cannot be said that there is a 
market.

  This also touches on web services management and configuration: the 
same (or similar) technology that a client entity uses to determine 
whether or not to invoke a given web service can also be used to 
automate the management and deployment of web services.

  Finally, looking forward to success, sorting out the semantics properly 
now may help with spamming of web services in the future. Having a close 
correspondence between a description of a service and its actuality will 
be a powerful weapon against spam.

Comment:
The modern approach to semantics can be characterized as being based on 
ontologies. The definition of the word Ontology is `the study of what is 
real' (my definition). More typically, in the computer industry, 
ontologies are short hand for dictionaries; where the definitional 
aspect is replaced by a graph of concepts.

What this means is that rather than trying to get at true meaning, which 
is harder than solving the halting problem, its enough to find an 
appropriate link in the graph of concepts to something that the program 
designer has hard-wired into the code. Using that trail it should either 
be possible for a program to `understand' a concept, or for it to have a 
reasonable basis to reject it. For example, looking for a Jaguar? It 
might help to know that the XJ6 is a Jaguar, and its a car; however, 
BigCat is a resident of San Francisco zoo (resident might be a 
hard-wired concept, animal is likely also, and SF is a city which is a 
place which is also hard-wired).

The graph technology used is subject to debate, (W3C appears to prefer  
RDF, others have more sophisticated choices), but that is not of the 
essence really. The ontology graph is separate from any description of a 
service, but an entity uses a combination of both to determine questions 
of the service (is it for me).

For web services, having the ability to read and digest a description of 
a service, is a big part of the technology needed to establish a fair 
automatic market.

Critical Success Factors for this goal:

D-AC024, D-AC025, D-AC026

D-AC026 ensures that a web service is properly characterized so that its 
semantics is clear to an automatic agent.

D-AC026.1 The Web Services Architecture should be aligned, where 
appropriate and possible with the Semantic Web. This may require some 
modification of current technology choices.

D-AC026.2 It must be possible to characterize the semantics of a web 
service, including elements within a choreographed service.
D-AC026.2.1 It must be possible to publish references to an ontology in 
a web service description
D-AC026.2.2 It must be possible to publish a description of the service 
using elements of one or more ontologies.
D-AC026.2.3 It must be possible to characterize a service using purely 
publicly observable semantics. I.e., the semantic description of a web 
service should not rely on private agreements or on unobservable 
characteristics of services and agents.
Received on Friday, 12 July 2002 18:23:36 GMT

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