- From: Brian McBride <bwm@hplb.hpl.hp.com>
- Date: Tue, 24 Jul 2001 11:48:24 +0100
- To: pat hayes <phayes@ai.uwf.edu>
- CC: w3c-rdfcore-wg@w3.org
pat hayes wrote: > > >Graham Klyne wrote: > > > > > > At 11:27 AM 7/19/01 +0100, Brian McBride wrote: > > > >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 > > > > > > > > > > > > > > > > > > There seems to me to be no way of rendering this statement using just > > > > > existential quantification. > > > > > > > >As you see, I've made an attempt. > > > > > > Good, thanks! > > > > > > The problem I now see is that this asserts the existence of the required > > > service: > > > > > > thereExists ?X which is the object of (advert123 description ?X) > > > (etc) > > > >I think the intent here was to assert the existence of the buyer service, > >which does exist (for some definition of exist). > > Look at the assertions in your example, above. There are two > existential claims made in there. One says that something (X) exists > which bears the description-1 (ie the inverse of description) > relation to advert123 and the product relation to roses and the > minQuantity relation to some other thing Y. X could be a 'service', > sure. But what kind of thing is Y? It bears a units relation to kg > and a minValue relation to 100. It sounds like a sale, or a > transaction, or maybe a quantity of roses. But whatever it is, the > sentences only assert that *one* of it exists. There is nothing here > that could possibly convey what is meant by the English gloss of "a > service that sells roses in quantities of at least 100 kg" (that is a > hell of a lot of roses, by the way) , since that gloss uses the > plural ("quantities"), but there isn't anything in the logical > version that implies more than one of anything. How about Y represents a range with a lower bound of 100Kg and an unspecified upper bound. Regarding the quantity of roses, my colleague must love her dearly or have done something very, very bad :) [...] > >What's a gensym error? > > Assuming that a formal structure means more than it really does just > because it seems to mean that when you read it as if it were English. > Comes from a famous AI paper by Drew McDermott where he suggested > that all 'intuitive' names be replaced by gensyms (LISP for genids) > before you try to figure out what the axioms mean. Ah - I recognise the paper from the description. > > > > > > > > > > > > > > > > This may be a compelling use-case, but I don't see any > >sanction for this > > > > > usage in M&S 1.0, and as such would suggest it be deferred to V2.0. > > > >Then you must show how it is different from the Lassila example in M&S. > > The difference is that the Lassila example is purely existential, but > this isn't. > > > > > > > > > > >What is the difference between this and the example in: > > > > > > > > > >http://lists.w3.org/Archives/Public/www-archive/2001Jun/att-0021/00-pa > >rt#41 > > > > > > That case asserts the existence of the un-identified individual. > > > >This case asserts the existence of an un-identified service. > > Fine; but what it says about it is that it is connected with the > existence of an un-identified quantity of roses. Not any such > quantity: just one. Not so - see above. Brian
Received on Tuesday, 24 July 2001 06:51:00 UTC