- From: David Allsopp <d.allsopp@signal.qinetiq.com>
- Date: Mon, 10 Mar 2003 13:37:27 +0000
- To: "Roger L. Costello" <costello@mitre.org>
- CC: www-rdf-logic@w3.org
"Roger L. Costello" wrote: > > Hi Folks, > > Here's how the OWL Reference defines the class Thing: > > <Class rdf:ID="Thing"> > <rdfs:label>Thing</rdfs:label> > <unionOf rdf:parseType="Collection"> > <Class rdf:about="#Nothing"/> > <Class> > <complementOf rdf:resource="#Nothing"/> > </Class> > </unionOf> > </Class> > > <Class rdf:ID="Nothing"> > <rdfs:label>Nothing</rdfs:label> > <complementOf rdf:resource="#Thing"/> > </Class> > > Isn't this a "circular definition", i.e., not very informative? /Roger Roger, The useful information is that a) Thing is not Nothing (and vice versa) b) All instances belong to the class Thing (and therefore no instances belong in Nothing) Looking closely at the definition of Thing, the class used in the unionOf could be any class - Nothing is used for convenience, so things (ahem) are not as circular as they seem; the definitions do actually capture the nature of the classes. E.g. Everything (all instances) is either Apple or NOT Apple - this would do just as well. Regards, David Allsopp -- /d{def}def/u{dup}d[0 -185 u 0 300 u]concat/q 5e-3 d/m{mul}d/z{A u m B u m}d/r{rlineto}d/X -2 q 1{d/Y -2 q 2{d/A 0 d/B 0 d 64 -1 1{/f exch d/B A/A z sub X add d B 2 m m Y add d z add 4 gt{exit}if/f 64 d}for f 64 div setgray X Y moveto 0 q neg u 0 0 q u 0 r r r r fill/Y}for/X}for showpage
Received on Monday, 10 March 2003 08:36:31 UTC