- From: <jos.deroo.jd@belgium.agfa.com>
- Date: Tue, 9 Oct 2001 00:56:27 +0100
- To: jjc@hplb.hpl.hp.com
- Cc: w3c-rdfcore-wg@w3.org
[...] > A: > > <uri> <pred> <uri2> . > <uri> <pred> <uri2> . > > was equivalent to one with only one: > > B: > > <uri> <pred> <uri2> . > > > This was intended as a harmless sort of comment :-(. > It was motivated by the graph abstract syntax. > > Under the model theory, we would say that two graphs are equivalent if they > mutually entail one another. > This would mean - wait for it Aaron :) - that > > C: > > <uri> <pred> <uri2> . > <uri> <pred> _:bnode . > > was another version of the same RDF model (if not the same RDF graph!). > From a model theoretic point of view A B and C are all equivalent. > This follows from the bnode being taken as an existentially qualified > variable. > > I assume that it would, in the fullness of time, be desirable to determine a > canonical RDF graph for any particular equivalence class of RDF graphs, for > instance, the equivalence class containing graphs corresponding to A, B, and > C would have canonical form B. This paragraph refers to the graph not to a > serialization of the graph. The canonicalization of the serialization of a > graph is known to be graph isomorphism complete. > > > If we consider an extension of C being: > > D: > > <uri> <pred> <uri2> . > <uri> <pred> _:bnode . > _:bnode <pred> _:bnode2 . > > then we can no longer ignore the second triple, since it is saying something > more substantive than the second triple in C. (after some bug corrections) we currently find that A simple-entails A A simple-entails B A simple-entails C B simple-entails A B simple-entails B B simple-entails C C simple-entails A C simple-entails B C simple-entails C D simple-entails A D simple-entails B D simple-entails C D simple-entails D and we *fail* to find that A simple-entails D B simple-entails D C simple-entails D -- Jos
Received on Monday, 8 October 2001 18:58:59 UTC