- From: Graham Klyne <Graham.Klyne@Baltimore.com>
- Date: Mon, 23 Jul 2001 22:06:32 +0100
- To: Brian McBride <bwm@hplb.hpl.hp.com>
- Cc: rdf core <w3c-rdfcore-wg@w3.org>
Brian, OK, I think I get it now. You're right about me committing the gensym error. (FWIW, it was "product roses" that got me. "productType roses" might have guided me around this pitfall.) I now accept that neither buyer nor seller service logically assert the existence of the product potentially transacted. So where does this leave the original discussion? I think we still have every anonymous resource being something whose existence is asserted. #g -- At 07:57 AM 7/23/01 +0100, Brian McBride wrote: >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 > > >This footnote confirms that this email message has been swept by >MIMEsweeper for the presence of computer viruses. ------------------------------------------------------------ Graham Klyne Baltimore Technologies Strategic Research Content Security Group <Graham.Klyne@Baltimore.com> <http://www.mimesweeper.com> <http://www.baltimore.com> ------------------------------------------------------------
Received on Monday, 23 July 2001 18:05:37 UTC