From: <jos.deroo.jd@belgium.agfa.com>

Date: Sat, 2 Jun 2001 19:24:28 +0100

To: ziv@unicorn.com

Cc: pfps@research.bell-labs.com, www-rdf-logic@w3.org

Message-Id: <OFB6DBA9C1.9D2E764F-ON41256A5F.005DEEA6@bayer-ag.com>

Date: Sat, 2 Jun 2001 19:24:28 +0100

To: ziv@unicorn.com

Cc: pfps@research.bell-labs.com, www-rdf-logic@w3.org

Message-Id: <OFB6DBA9C1.9D2E764F-ON41256A5F.005DEEA6@bayer-ag.com>

> I am beginning to lose sight of what the terminology "ground facts" > is supposed to mean in this context. > > At the risk of being a considered a dreary pedant, I will sketch out > here how I was taught one constructs a logic, and then ask where this > fits into the terms of the debate raging in this interests list: > > a. Determine a group of "logical" symbols that are "reserved" and > assumed to be a part of any language that one will define and > use -- this is where connectives, quantifiers, modal operators, > etc. are declared, perhaps also variables > > b. Determine that a language may contain "non-logical" symbols that > play the roles of relations, or functions, or constants etc. > > c. Determine rules for deciding what constitutes a well-formed > statement built out of these logical and non-logical symbols > > d. At this point, either build a proof theory or a model theory > or both. For a proof theory, declare logical axioms and rules > of inference that enable one, given certain statements as assumed, > to infer other statements as conclusions. For a model theory, one > needs to explain how and when statements in the language are to > be considered "satisfied" in possible worlds or structures or models, > etc. > > What are "ground facts" this picture? Where in this picture does RDF > fit in? Where would another language "built atop RDF" fit in? Or is > all this irrelevant to the debate? Let us try (and this is not intended as 'hardcore') (and modulo syntax issues) [[ We've got terms of the form _:name for "anonymous" terms <absURIref> for URIs "lskdjf" for string literals. and statements of the form S P O. where S, P, and O are terms (S and P can't be literals in the expected results from any RDF 1.0 document.) ]] -- http://lists.w3.org/Archives/Public/w3c-rdfcore-wg/2001May/0264.html Logical conjunction is just juxtaposition of statements. So far that is what one maybe could call RDFCore. "built atop RDF" could be DAML based languages. and First Order Logic as per http://www.w3.org/2000/10/swap/log.n3 log:implies for logical implication log:forSome for existential quantification log:forAll for universal quantification log:Truth for assertion i.e. stmt a log:Truth. log:Falsehood for negation i.e. stmt a log:Falsehood. I would say that ground facts are Horn-clauses with one positive literal. -- Jos De Roo, AGFA http://www.agfa.com/w3c/jdroo/Received on Saturday, 2 June 2001 13:24:55 UTC

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