- From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
- Date: Tue, 02 Oct 2001 17:06:42 -0400
- To: tpassin@home.com
- Cc: www-rdf-logic@w3.org
From: "Thomas B. Passin" <tpassin@home.com> Subject: Re: Literals (Re: model theory for RDF/S) Date: Tue, 2 Oct 2001 16:37:17 -0400 > [Peter F. Patel-Schneider] > > > From: Patrick.Stickler@nokia.com > [...] > > > Again. If you require that DIFFERENT URIs denote DIFFERENT things you > > cannot later turn around and allow any two different URIs to denote the > > same thing. You have already said that they denote different things, and > > this would introduce a contradiction. > > > > > I'm not against such a URI equivalence mechanism, I just don't (at the > > > moment) see it belonging at the fundamental RDF layer. Maybe it *does* > > > belong there, but I'm not convinced. > > > > This has nothing to do with whether RDF has any mechanism for equivalence > > or difference. It has to do with whether anything built on top of RDF can > > ever have a non-trivial theory of URI or literal equivalence. > > > > Let's not forget the inverse case. Many people will want to use RDF > ***without*** another layer on top, like DAML+OIL, and it must be usable for > them too. This supports the need for a good understanding of the > (semantic?) level at which new extensions, etc., should be applied, > otherwise things that properly belong in higher layer will get thrown into a > lower, and the reverse. Agreed. > For example, the syntactic equivalence of two URIs can be determined > according to the normalization rules for URIs, and clearly belongs in RDF. > RDF is supposed to have a datatype system, so it's reasonable to expect it > to be able to tell strings from integers, but you can't apply that to > literals because they can't be the subject of statements (unless that rule > gets changed). Also agreed, but I sense that there are quite a number of people that are not in favour of RDF having a datatype system. > So if I want to use RDF without a higher layer, I have to take all literals > as is, just as labels, or do my own private processing on them. > > To me, this is inconsistent with the idea that RDF can make statements about > "anything". Without a higher layer, I can't make a statment about the > nature of a literal. I'm also not sure I can tell the difference between a > URI string used as a literal value, and one used as a Resource-indicating > URI. > > I suggest, then, that RDF is the right layer for resolving this particular > issue (depending, of course, on how you end up fixing it). Also agreed. Further, the only reason that DAML+OIL has its own datatype mechanism is that there is not one in RDF(S). > Forgive me for thinking while I type, but things are slowly getting clearer > for me! > > Cheers, > > Tom P Peter F. Patel-Schneider
Received on Tuesday, 2 October 2001 17:07:32 UTC