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Re: DAML+RDFS: potentials for simplifications?

From: Wolfram Conen <conen@wonkituck.wi-inf.uni-essen.de>
Date: Thu, 29 Nov 2001 17:40:49 +0100 (MET)
Message-Id: <200111291640.RAA28180@wonkituck.wi-inf.uni-essen.de>
To: jbroeks@cs.vu.nl (Jeen Broekstra)
Cc: www-rdf-interest@w3.org
Interesting issue.

> I am also unsure whether this idea of flexible addition of
> expressivity is feasible at all. The problem to me seems to
> be that you need a starting point that is itself at least as
> expressive as the language that you are trying to "learn",
> which kind of defeats the purpose of the undertaking.

Hm, what exactly is the purpose of the undertaking?  
Let me point out a simple possibily: why don't we 
agree upon one (or a set of) "host formalism(s)" 
that gives us the expressivity required to develop
RDF vocabularies and RDF-based applications easily
and interchangably - perhaps taken out of the 
datalog (or Ur-datalog) family. With a minimal 
hardwired transformation (for example: from triple
to a 3-ary predicate), semantics of properties 
could then be defined "on the fly" (as needed
by the application-domain community developing it)
by giving a definition of the property embedded
into RDF in a suitable codification of axioms -- 
this can be done with embedded RuleML or 
RDF-encoding of rules a la McDermott, for 
example (or a XML-serialization of S-KIF
or whatever -- even alternatives in one document
for different host formalism are possible). 
Then, we could start to develop semantically
-augmented RDF schemata based on sufficiently
expressive (though, admittedly potentially 
expensive) and well-known formalisms, we may
even run into undecidability problems once
in a while (depending on the chosen formalisms),
but we would have something that is easy to use
for a number of developers, and that can drive
the evolution of RDF vocabularies and applications. 
(We could later still decide to reduce the 
possibilities again if that should be necessary).
We can then use a mapping of DAML or RDFS to suitable
formalisms and schemata that are augmented accordingly
with axioms expressed in this formalism to restrict 
expressivity to some commonly agreed upon "language" --
but we can also easily add/change/augment semantics 
to application-specific needs, experiment with other
subset-languages of the chosen host formalism on the
fly, may even come to something as a competition of
vocabularies etc.

We can, of course, continue to reinvent the wheel of 
logic for RDF*/RDFS/RDF++ anew and keep the whole 
SemWeb-(r)evolution stalked a bit longer ;-) 


(*: Brief remark: If we do so, I am not sure if assuming
that RDF is not a convention to speak in subject/
predicate/object patterns (with the possibility to
interpret reification as a means to build nested 
structures etc.) but a logic language asserting 
instances of binary relations, is really helpful 
- but that's another topic).

PS: of course, embedding axioms in RDF and "interpreting" RDF/RDFS inside of
a host formalism, has been suggested earlier (Staab et al, Conen/Klapsing,
I can give precise references if needed, simply send me an email),
but I've never really seen a discussion of it. If I missed it, please, send
me a pointer. Thanks.
Received on Thursday, 29 November 2001 11:40:51 UTC

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