- From: Brian McBride <bwm@hplb.hpl.hp.com>
- Date: Mon, 23 Jul 2001 07:57:32 +0100
- To: Graham Klyne <Graham.Klyne@Baltimore.com>
- CC: rdf core <w3c-rdfcore-wg@w3.org>
Graham Klyne wrote: [...] > I'm fine with asserting the existence of the buyer service. The problem I > have is that the *description* of the buyer service asserts the existence > of something that may not actually exist. I'm obviously not being clear. In > >Loosely in English it means advert123 is for a service that will > >buy roses in quantities of at least 100. > > > > advert123 role buyer > >and thereExists ?X advert123 description ?X > > ?X product roses > > thereExists ?Y ?X minQuantitiy ?Y > > ?Y units kg > > ?Y minValue 100 > > ?X denotes a service that will BUY roses in minimum quantities of 100kg. There does exist a service that can be bound to ?X. Its the buyer service. That's what we're advertising here. Or was it ?Y you were suggesting could not be satisfied. > > > > But the apparent intent of this is ask if such a service exists. Do I > > > detect a "gensym" error? > > > >What's a gensym error? > > An expression Pat used recently, if I get it right, to describe logical > errors introduced by human interpretation of a symbol in an expression > without any logical basis for that interpretation. Then I'm hoping you have now :) > > In this case, we know what a "buyer" is, and what a "seller" is. > > The two examples you gave in > http://lists.w3.org/Archives/Public/w3c-rdfcore-wg/2001Jul/0240.html are > identical modulo a name change and a quantity. (Pedagogically, they could > equally have been stated using the same quantity so that the only > difference was a name change.) > > Yet we infer that in one case the goods offered for sale definitely exist, > but in the other case no assertion is made about their existence. There > seems to be no *logical* basis for this difference in interpretation when > the only difference is a naming difference. > > Currently, it seems to me that the Existential-Conjunctive (EC) subset of > first order logic, hence RDF as I understand it, is incapable of expressing > the buyer proposition without actually asserting the existence of that > which is to be purchased. Of course it can. If it can assert that a seller service exists, surely it can equally well assert that a buyer service exists. It doesn't know the difference. Brian
Received on Monday, 23 July 2001 03:00:19 UTC