- From: Markus Lanthaler <markus.lanthaler@gmx.net>
- Date: Mon, 18 Feb 2013 19:36:43 +0100
- To: "'Eric Prud'hommeaux'" <eric@w3.org>
- Cc: "'Andy Seaborne'" <andy.seaborne@epimorphics.com>, <public-linked-json@w3.org>, "'RDF-WG'" <public-rdf-wg@w3.org>
On Monday, February 18, 2013 7:08 PM, Eric Prud'hommeaux wrote: > > Yes. Would that also be the case if bNodes would *not* denote the > graph they > > label? As I understand it, if bNodes wouldn't denote the graph, you > couldn't > > look up a graph labeled with a bNode ID in a dataset because you > wouldn't > > know if that bNode ID denotes that graph or not. Is that correct? > > Aha! Would "does not formally denote the graph" mean there's no usable > mapping from label to graph? I believe we can factor out whether > bnodes are permitted as graph labels as this question is arises in > either case. I think it does. I think that's exactly the problem that Pat outlined in one of his previous emails: http://lists.w3.org/Archives/Public/public-rdf-wg/2013Feb/0096.html > > If you have the following dataset: > > > > { > > _:b1 x:signature "... signature ..." . > > } > > _:b1 { > > ... some triples ... > > } > > > > Do the two _:b1 above refer to the same, i.e., the named graph? Does > this > > mean that "... signature ..." is the signature of the graph labeled > with > > _:b1? Or could it be that the signature is about something completely > > different? > > Yeah, it'd really be useless if the system were permitted to have _:b1 > (or even <http://a.example/graphs/b1>, for that matter) refer to > something other than the graph which was paired with that signature. Unfortunately, I think that's the case for http://a.example/graphs/b1. > I don't know how to utter that in the semantics doc 'cause I don't > know what "denotes" means. The semantics that we're trying to avoid > implying is that dataset1's graph <foo> is the same as dataset2's > graph <foo>. (Some systems may make such a promise, but it's not > generally required of e.g. deployed linked data or SPARQL systems.) Why's that? Why does "foo" not identify (to use a different term) the graph. The two datasets may contain the same triples of the graph "foo", or maybe just a subset of them. Why is this different from an IRI in the subject position? > All the semantics has to capture is that for a given dataset, there is > a map from graph label to graph. I suspect we don't want to go a > step further and say that the mapping is 1:1 because of: > > { > <b1> dc:author "Bob" . > <b2> dc:author "Bob" . > <b1> owl:sameAs <b2> . > } > <b1> { ... some triples ... } > <b2> { ... some triples ... } What would be the problem if we would do that? > I suspect that saying > > Within a dataset, a graph node label denotes a graph. > Graph node labels may appear as subjects or objects in graphs. > > would do the trick, but again, I don't understand what drove us from > "denotes" to "is paired with". Neither do I.. I'm trying to find it out because I find it very confusing and inconsistent. Thanks for your patience. I know this all has already been debated to death but I wasn't able to find any arguments baking the decision up (apart from "the SPARQL WG is silent about it"). -- Markus Lanthaler @markuslanthaler
Received on Monday, 18 February 2013 18:37:16 UTC