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DAML-S 0.6: use of classes vs instances

From: Dickinson, Ian J <Ian_Dickinson@hp.com>
Date: Tue, 27 Nov 2001 14:38:32 -0000
Message-ID: <5E13A1874524D411A876006008CD059F15CA33@0-mail-1.hpl.hp.com>
To: "'www-ws@w3c.org'" <www-ws@w3c.org>
Folks -
A Jena user asked a question about Jena support for DAML-S, and pointed me
at the latest version of the specs on
http://www.daml.ri.cmu.edu/ont/DAML-S/Release0.6/. Since I wasn't familiar
with the details of DAML-S, I've spent a little time trying to get up to
speed.  I'm sure I'll have a number of questions, but one leaps right out at
me from reading the Congo and Bravo Air examples.

In essence it is this: where's the data?

To be more precise, I notice that all of the definitions are for DAML
classes and properties. Nowhere are instances defined, or actual RDF triples
giving the properties of the instances. So when congo.daml says:

<daml:Class rdf:ID="CongoBuy">
  <rdfs:subClassOf rdf:resource="&process;#AtomicProcess"/>
</daml:Class>

this tells me that there is a DAML class CongoBuy, all instances of which
are also instances of AtomicProcesses, but it doesn't tell me that there is
an individual CongoBuy service that I can interact with.  Similarly:

<rdf:Property rdf:ID="congoBuyCreditExistsPrecondition">
  <rdfs:subPropertyOf rdf:resource="&process;#precondition"/>
  <rdfs:domain rdf:resource="#CongoBuy"/>
  <rdfs:range rdf:resource="#CreditExists"/>
</rdf:Property>

says that there can be statements relating instances that are CongoBuy's to
instances that are CreditExists, and that the set of pairs that define
'congoBuyCreditExistsPrecondition' is a subset of the set of pairs that
define 'precondition', but not that a given CongoBuy service has the
precondition that CreditExists.

I could use all this information to *validate* any RDF data I could find
that described one or more CongoBuy services, but I don't see how I could
find Congo and actually buy a book without some instance data.

Equally plausibly, I've completely missed the point :-)   All comments
welcome.

Thanks,
Ian
Received on Tuesday, 27 November 2001 09:38:45 GMT

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