- From: Sandro Hawke <sandro@w3.org>
- Date: Fri, 30 Sep 2011 15:11:36 -0400
- To: Richard Cyganiak <richard@cyganiak.de>
- Cc: Pierre-Antoine Champin <pierre-antoine.champin@liris.cnrs.fr>, "public-rdf-wg@w3.org" <public-rdf-wg@w3.org>
On Fri, 2011-09-30 at 12:02 +0200, Richard Cyganiak wrote: > > > (imagine for example a owl:sameAs statement between two graphs IRI > in a > > SPARQL engine supporting OWL inference; what would that mean?) > > owl:sameAs means that two terms denote the same resource. As written > in the ED, use of those terms as graph names is entirely orthogonal to > that. > > I think that's a good thing. Named graphs are key to trust and > provenance. Trust and provenance must happen at a lower level in the > stack, before reasoning and inference kick in. W3C's version of the > layer cake, where trust sits above reasoning, cannot work. The moment > you reason with OWL over untrusted data, you [have problems]. I don't think we need to throw out reasoning on the fourth column. As long as we're careful about what it means -- eg: it denotes an IR which may give you a Graph -- I think people are free to layer inference and trust/provenance reasoning in various ways. Let's say you are using three Web data sources, S1, S2, and S3. S1 and S2 give just triples. S3 is an ontology (perhaps a RIF document); we don't really care if it's triples. What's the problem with merging the triples, doing the inference, and using the result, knowing it is no more trustworthy than the least of S1, S2, and S3? Specifically, the provenance of your output involves the provenance of S1, S2, S3, and the reasoning steps you took. In detailing those reasoning steps, I think the identifiers for S1, S2, and S3 will be useful. Perhaps your point is that if the reasoning on the data from S1, S2, and S3 starts to do things with the identifiers for S1, S2, and S3, like say S1=S2, then, yes, things get very tricky. Self-reference. Danger. But for a later-stage provenance system to reason about S1, S2, and S3 is fine, I think. -- Sandro
Received on Friday, 30 September 2011 19:11:48 UTC