- From: Graham Klyne <Graham.Klyne@Baltimore.com>
- Date: Thu, 26 Jul 2001 20:27:02 +0100
- To: pat hayes <phayes@ai.uwf.edu>
- Cc: w3c-rdfcore-wg@w3.org
Pat, I think this discussion harks back to an earlier one, about creating a new language with core RDF as a subset (except, possibly, for some special properties that are not available for the normal interpretation). I think this is probably getting out of scope for this forum, but I'd love to have a "corridor/bar discussion" with you about this in Stanford/Sebastopol. #g -- At 12:02 PM 7/26/01 -0700, pat hayes wrote: >>At 10:15 PM 7/23/01 -0700, pat hayes wrote: >>>It isnt clear to me what the scope of anonymous node is intended to be, >>>but it if it is the document containing the node, then indeed it should >>>be impossible for any other source to say anything about the thing it >>>refers to, so this is a genuine difference. However, the same is true of >>>a non-anonymous URI if its use is restricted to this one source. >> >>I've been thinking recently about encoding inference rules in RDF, where >>a rule may have a variable that is scoped by the rule; e.g. >> >> Dog(?x) -> Animal(?x) > >OK, you have left me behind already. I don't see any way to get anything >remotely like that into RDF. I presume this is supposed to mean that for >any ?x, if it is a dog then it is an animal, right? How do we encode >universal quantifiers in an exist-conj logic like RDF? > >>Originally, I was thinking that, when encoding this in RDF the variable >>represented by ?x must somehow be scoped within the RDF. But when I >>started looking at candidate RDF encodings this need for scoping just >>melts away: the variable is represented by a new, unique resource: > >??? Wait. Resources are the things in the world, the things that are >denoted by URI's, right? One doesnt get quantification by putting >variables into the *domain* (whatever that means: I'm not sure what it >means, to be honest. ) > >>that resource has global scope (and, hence, if it has a URI it is one >>that is not shared by any other resource). The only place where the >>concept of scope is needed is in the original expression. Some other >>expression; e.g. >> >> Cat(?x) -> Animal(?x) >> >>Has a different scope for its ?x, but the resource that represents the >>variable in the encoding of this is a different resource than the one >>that represents ?x in the previous example. > From this exercise, I tentatively suggest that the scope of any >>resource (node) is global -- the entire universe of discourse. > >Well, I think I follow your point, and indeed one can do something like >this in conventional logic, where its often called 'standardizing apart', >ie no variable name is ever used twice, so there is no risk of getting >them confused. But (1) it is unworkable in practice, and (2) you still >need some way to indicate, or determine, the scopes. For example, consider >the difference between >foo & (cat(?x) -> animal(?x) ) >and >(foo & cat(?x)) -> animal(?x) > >>(I'm trying to be clear that this is an encoding of inference rules in >>RDF, not an attempt to make inference rules part of RDF.) > >Maybe this is my problem. I'm not sure what this distinction amounts to. >RDF has a 'meaning' already, so how does one get its meaning changed so it >can do this encoding for you? > >Pat Hayes > >--------------------------------------------------------------------- >(650)859 6569 w >(650)494 3973 h (until September) >phayes@ai.uwf.edu http://www.coginst.uwf.edu/~phayes > > >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 Thursday, 26 July 2001 15:33:47 UTC