From: Dan Connolly <connolly@w3.org>

Date: Fri, 02 Feb 2001 17:26:22 -0600

Message-ID: <3A7B421E.CCCD9C5A@w3.org>

To: Miles Sabin <MSabin@interx.com>

CC: www-rdf-logic@w3.org

Date: Fri, 02 Feb 2001 17:26:22 -0600

Message-ID: <3A7B421E.CCCD9C5A@w3.org>

To: Miles Sabin <MSabin@interx.com>

CC: www-rdf-logic@w3.org

Miles Sabin wrote: > > Dan Connolly wrote, > > pat hayes wrote: > > > according to several members of the group which developed > > > RDF, the 'graph model' of a set of RDF triplets is intended > > > itself to be *the* model (in the sense from model theory) of > > > those triplets. > > > > Really? can you cite a source for that? I'd like to correct it. > > Correct what? That the intended model is the graph/triplet model; > or any implication that there's a model (in the model-theoretic > sense) at all? That there's a model-theoretic model in the RDF spec at all. > > I'm just sort of teaching myself all this model theory stuff > > as I go, but as far as I understand it, the semantics of RDF > > are just like the semantics of first-order logic, where the > > only terms are URIs (constant symbols) and existentially > > quantified variables, and the only formulas are ground > > propositions, conjuctions, and existentially quantified > > formulas. > > That seems more or less right to me, with the following two > qualifications, > > * There are no conjunctions in the way there are in typical > languages (tho', to be sure, you can get something like the > effect of asserting P&Q by asserting P and asserting Q). well... ok... > * Even if there's no explicit formal model, there's a fairly > clear indication in RDF M&S that the quantifiers range over > resources, ie. things which have a URI, Huh? which part of the spec suggests that every resource has a URI? Consider: <rdf:Description> <foaf:workEmailAddress resource="mailto:connolly@w3.org"/> </rdf:Descrption> aka (exists (?x) (foaf:workEmailAddress ?x mailto:connolly@w3.org)) ?x is me, right? i.e. the quantifiers might range over anything you like. I think I could construct descriptions of transcendental numbers similarly. I think the RDF spec leaves open the size (cardinality) of the domain of discourse. > hence that the domain > of quantification is at most countably infinite ... because > there at most countably many URIs and no two distinct resources > can share a URI. That would follow, but I don't accept the premise. > BTW, if you're looking around for an interesting logical > framework to embed RDF M&S, I'd recommend, > > _A_Structuralist_Theory_of_Logic_, Arnold Koslow, > Cambridge University Press, 1992 er... ouch! $95.00 at amazon. Is there anything online that explains it? > _extremely_ highly. The salient point is that he manages to > crank a variety of first order logics (both classical and non- > classical) and a framework for building modal logics, out of > resources which aren't all that different from what RDF M&S has > to offer (I can elaborate on this if anyone's interested ... with > the caveat that I'm an ex-philosopher, not a logician). > > Cheers, > > Miles -- Dan Connolly, W3C http://www.w3.org/People/Connolly/Received on Friday, 2 February 2001 18:26:25 UTC

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