- From: Brian McBride <bwm@hplb.hpl.hp.com>
- Date: Mon, 21 May 2001 16:27:55 +0100
- CC: w3c-rdfcore-wg@w3.org
Graham Klyne wrote: > > I kind of like this general approach, but there's one thing I would pick up > on at this point... > > I would say there is a mapping D : (RxP) -> E, where "P" is some arbitrary > set of parameter data. I think something like this is needed to capture > the idea that there may be an arbitrary number of entities associated with > a resource, varying over time, content negotiation, location, identity of > enquirer, etc., etc. I agree with this. I left it out for simplicity. I think of D as a lambda expression of your function with the P arguments bound in. This also extends to define a meaning for reification. Given a resource RS, which is a reified statement, then D(RS) = (p, s, o) for some p, s and o. > > D((p,s,o)) <=> D(p)(D(s),D(o)) > > I don't follow this last bit. Yes, got that bit wrong. What I had in mind was define an interpretation function for statements. There is an Interpretation Function I : Statements -> REL that I((p,s,o)) = D(p)(D(s),D(o)) where REL is the set of binary relations D(R) x (D(R) u L), L = the set of literals, which, forgiving a little slopiness of expression, is basically saying that a statement is interpretted as an relationship between a resource and either another resource, or a literal. And of course: I({s1, s2, ... sn}) = I(s1) & I(s2) & ... & I(sn) Which is how I make sense of some of the recent discussions on RDF logic re reification. What does the following mean, i.e. what is that value of I: {(rdf:type, rs, rdf:Statement), (rdf:subject, rs, theSky), (rdf:predicate, rs, hasColor), (rdf:object, rs, blue), (foo:signedBy, rs, Brian)} D(rs) = (hasColor, theSky, blue) so we have: D(foo:signedBy)(D(rs), D(Brian)) & ... [omitting unnecesary bits - i.e. handwaving] = D(foo:signedBy((hasColor, theSky, blue), D(Brian)) Which is not the same as; D(foo:signedBy(D(hasColor)(D(theSky), D(blue)), D(Brian)) Certainly one of the issues that keeps coming up on RDF logic is that a way to represent both of the above expressions is needed, and they perceive that RDF only gives them one. Brian
Received on Monday, 21 May 2001 11:28:24 UTC