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Re: What do the ontologists want

From: Sandro Hawke <sandro@w3.org>
Date: Fri, 18 May 2001 06:29:53 -0400
Message-Id: <200105181029.GAA03482@hawke.org>
To: pat hayes <phayes@ai.uwf.edu>
cc: www-rdf-logic@w3.org

pat hayes:
> sandro:
> >For example, I might want tell some entity that if it has the triple
> ><A,B,C> in its store, it should remove it.  I want to say something
> >like:
> >
> >   there exists some triple T with a first
> >   element A, a second element B, and a
> >   third element C.  If you currently believe
> >   T to be true, forget that fact.
> 
> I have NOOO problem with you doing that, let me emphasise.

And then you go on to say, as I understand it, that the language of
triples is not very expressive.  There are lots of things you can't
say in it directly.  When you want to say such things, you'll have to
build the syntactic structures of a more expressive language by
describing them in these little RDF triples.

Which I agree with entirely.  And I think this somewhat-painful
layering approach is probably good software engineering.  We can
standardize on triples relatively easily (as long as we understand
that's what we're doing).  And triples themselves are expressive
enough for a lot of information, like much of what people are putting
into XML or relational databases.  This is probably not KR research
material.

And with triples standardized, people can build their more-expressive
logical languages on the somewhat more abstract cons-cells of triples
instead of directly on byte strings.  I imagine this will be useful in
very roughly the way that LISP seems to be better for building AI/KR
systems than C: you can avoid worrying about concrete syntax and the
semantics of simple stuff.  And more: you should get nice,
interoperable libraries, without namespace collisions, because of the
other aspect of RDF triples: the fact that the symbols are handed out
in a way which avoids unintended reuse.

(Some people also want the symbols to contain (or be) a pointer to
some definitional truth.  I'm still skeptical about that.)

> set of triples will be) and we will probably need a few 
> datastructuring primitives (like end-of-chain markers, cf. Lisp NIL.) 

Yeah -- that's one of those silly-but-necessary bits DAML does, of
course.  Now other people building KR languages on RDF don't need to
reinvent that.  (not that it would be too hard....)

>                                                        There isnt 
> anything odd or exotic about all this, let me emphasize: its is just 
> ordinary bread-and-butter datastructure design.

Mostly agreed.  Building data structures on triples is somewhat
different from building them with pointers in memory because of
multi-valued slots and incomplete structures.  But if you decide not
to use that flexibility, and don't even look at the structure until
everything you want has cardinality=1, then yes I agree it's all bread
and butter.

    -- sandro
Received on Friday, 18 May 2001 06:30:03 UTC

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