Re: How do RDF and Formal Logic fit together?

From: "Pat Hayes" <phayes@ai.uwf.edu>

Sandro Hawke:  Something we might like to add to RDF, to make it more
expressive, is logical negation.   How would you extend RDF's syntax to
handle it?  Lay on another language, which is interoperable with RDF.  Say
in an RDF graph syntax.

PH:   Why in an RDF graph syntax? (What is so special about RDF? Its one
among thousands of possible notations, and its not a particularly good one.
The limitations of simple graphs as a notation have been known for about a
century, so why would we want to deliberately go back to the stone age to
find a basis for the world wide web? )

SR: I would like to know specifically what those limitations are ... I have
not found any.

PH: No way to indicate scope or variable bindings, chiefly.

SR: Well actually there is if you will allow that a scope of a variable can
be specified by a set of statements and that statements themselves have
identity.

PH: OK, no way to indicate a set of statements. Same thing.

SR: Well actually there are two ways to do that.
[snip ..]

PH:  Neither of these is possible in RDF, however. RDF uses triples, not
quads; it has no mechanism or notation for attaching identifiers to
statements; and it requires arc labels to be urirefs, not pairs of
anything. Of course there are extensions of RDF in which all manner  of
things can be written, but this is the RDF-logic list, not the  RDF++-logic
list.

SR:  Seems we have come full circle here and cannot extend RDF to a graph
syntax that is interoperable with RDF because of the limitations of simple
graphs, but cannot remove those limitations because then it would not be
RDF.

.... wiggy woggy woo ...

Seth Russell

Received on Wednesday, 24 October 2001 21:04:50 UTC