- From: Peter F. Patel-Schneider <pfpschneider@gmail.com>
- Date: Fri, 16 Dec 2022 11:21:56 -0500
- To: public-rdf-star-wg@w3.org
Suppose there are two RDF graphs, each available on the web at well-known sites, i.e., many people would believe that they are part of the linked data cloud. The first graph contains at least the following triple: <http://example.com/kennedy> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://dbpedia.org/ontology/Person> . The second graph contains at least the following triple: <http://example.com/kennedy> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://dbpedia.org/ontology/Place> . If IRIs denote the same thing everywhere then it seems to me that everyone is committed to <http://example.com/kennedy> being an instance of both <http://dbpedia.org/ontology/Person> and <http://dbpedia.org/ontology/Place>. There is no problem in RDF or RDFS with this being the case, but I don't think that it matches most peoples' understanding of any world close the world that we live in. In my view one should say something more like: When combining RDF graphs, IRIs are combined as-is but blank nodes generally need to be renamed so that there are no collisions between the blank nodes from different graphs. Blank nodes absolutely do denote, just like global existential variables denote. It is just that what they denote is in some sense less determined than what IRIs denote. peter On 12/16/22 09:10, Antoine Zimmermann wrote: > > > Le 16/12/2022 à 12:58, Pierre-Antoine Champin a écrit : > >> that means the same everywhere. > > just like an IRI, a literal or a blank node means the same everywhere > (mind you, I'm talking about blank nodes, not blank node identifiers, who > have a local scope). > > What do you mean by "a blank node means the same everywhere"? > Literals and IRIs denote the same thing everywhere, yes. Conversely, bnodes > do not denote anything. Bnodes only indicate the existence of things, and > what thing exists as indicated by a bnode depends on the RDF graph being > considered. > > It happens that the CG report interprets quoted triples as bnodes whose > identity depends on the RDF-star graph being considered. So if you consider > different RDF-star graphs containing the same quoted triple, the quoted > triple in the context of the first graph indicates the existence of a > different things than the quoted triple in context of the second graph. > > See https://w3c.github.io/rdf-star/cg-spec/editors_draft.html#mapping item > 2.2).
Received on Friday, 16 December 2022 16:22:10 UTC