- From: pat hayes <phayes@ai.uwf.edu>
- Date: Mon, 23 Jul 2001 19:40:52 -0700
- To: Graham Klyne <Graham.Klyne@Baltimore.com>
- Cc: w3c-rdfcore-wg@w3.org
>At 08:16 PM 7/16/01 -0500, Aaron Swartz wrote: >>On Monday, July 16, 2001, at 02:48 PM, Graham Klyne wrote: >> >>>E.g. when exchanging RDF between systems (the reason for >>>standardization), do we really want to specify that the existence >>>of a node, without properties, is significant? If so, we must >>>define the significance, and that looks awkward to me. >> >>Can you explain why this seems awkward to you? It seems like a >>perfectly reasonable thing to do to me. >> >>The alternative seems to declare that: >> >><rdf:Description rdf:about="foo" /> >> >>means: >> >><foo> rdf:type rdfs:Resource . >> >>which seems even more awkward. > >Actually, I think that is a relatively painless way of interpreting >nodes without properties (one that I hadn't thought of). > >The "awkwardness" to which I refer is: > >(a) how is one to represent such a node in N-triples? Currently, >there's no obvious way (apart from what you suggest above). > >(b) having selected an N-triples representation, some kind of >semantics must be defined -- it seems rather pointless to take >special steps to define a form and then say it adds nothing to the >meaning. > >That said, I think your suggestion above quite neatly addresses both >concerns (assuming that semantics for any triple of the form: > > <foo> rdf:type <bar> . > >must be defined). Right; the obvious (I should know better than to say that) interpretation of a 'bare' name is that it says that a thing exists with that name, which is usually vacuous, so harmless. And this is what <foo> rdf:type rdfs:Resource seems to say as well, in a kind of reified way where having an rdf:type is like having the property of existing somewhere in the domain. So the obvious (?) semantics for this would say that the extension of I(rdf:type) has to be a subset of Rx(2|R) and that <x, y> is in EXT(I(rdf:type)) just when x is in the set y. This provides a general-purpose way to say that something is in a subset of the universe - provided of course that the subset in question has a name - and then the case in question has y being the universe itself (which is required to be the denotation of rdfs:Resource, I presume) , so the assertion just says that x exists, which is always true. Pat --------------------------------------------------------------------- (650)859 6569 w (650)494 3973 h (until September) phayes@ai.uwf.edu http://www.coginst.uwf.edu/~phayes
Received on Monday, 23 July 2001 22:40:46 UTC