- From: Pierre-Antoine Champin <pierre-antoine.champin@liris.cnrs.fr>
- Date: Wed, 29 Jun 2011 10:02:09 +0200
- To: "antoine.zimmermann@insa-lyon.fr" <antoine.zimmermann@insa-lyon.fr>
- CC: "public-rdf-wg@w3.org" <public-rdf-wg@w3.org>
Antoine, On 06/28/2011 12:07 PM, Antoine Zimmermann wrote: > Pierre-Antoine, > > Le 22/06/2011 19:19, Pierre-Antoine Champin a écrit : >> Hi all, >> >> after today's telecon, I read the proposal at [1]. >> >> First, it seems to be a "light" version of the Named Graph paper that >> Pat mentionned. "Light", because it specifies that >> >> "The interpretation of the IRI [paired to graphs], in the RDF Semantics >> sense, is left unspecified." >> >> It is all very well, but what happens when one wants to use those IRIs >> *in* the named graphs? As proposed in the 'Semantic Extension' section >> of [1]? > > This section, which I wrote, was put there before we made any decision > on what the naming mechanism of graph store means. This section should > be considered informative, explaining how the basic semantics can be > extended. Such extension /may/ be defined externally to this WG. > > The semantics is extremely simple and does not make any assumption on > what the "name of the graph" means. The graph name is just used as an > indice in a family of graphs. I'm affraid you can not avoid to make that assumption. If I follow you, :G1 graph:imports :G2 . would "only" mean the graph associated with URI :G1 imports the graph associated with URI :G2 (for some given association which is not *naming*) Now assume that you know that :G2 owl:sameAs :G3 . Nothing prevents you from infering now that :G1 graph:imports :G3 . But the graph associated with URI :G2 may be completely different from the graph associated with URI :G3 ! The problem comes from the fact that, to avoid the "graph naming assumption", we need a property to talk about the URIs (and indirectly, about the graph associated with them) while RDF properties always talk about the resources denoted by the URIs. If we used *resources* as graph identifiers, then it would be different. But unfortunately, that is not what SPARQL is doing. pa > > >> >> Stating >> >> :G1 graph:imports :G2 >> >> does make some assumption about the meaning of :G1 and :G2 in the RDF >> Semantics! More generally, if we want to make graphs first class >> citizens of RDF, we need a mean to talk about them, hence we need IRIs >> whose interpretation in RDF Semantics is that graph. >> >> pa >> >> >> [1] http://www.w3.org/2011/rdf-wg/wiki/TF-Graphs/RDF-Datasets-Proposal >> > >
Received on Wednesday, 29 June 2011 08:02:43 UTC