- From: Antoine Zimmermann <antoine.zimmermann@insa-lyon.fr>
- Date: Fri, 15 Apr 2011 11:18:20 +0200
- To: Pat Hayes <phayes@ihmc.us>
- CC: RDF Working Group WG <public-rdf-wg@w3.org>
Le 14/04/2011 23:50, Pat Hayes a écrit : > > On Apr 14, 2011, at 2:36 PM, Antoine Zimmermann wrote: > >> Our decision today was about SPARQL datasets and what the URI in >> the <n,G> pairs is referring to. We said it does not necessarily >> identify the graph in the sense of what the RDF semantics says (the >> interpretation of n does not need to be the graph). This is enough >> to define a notion of interpretation and model of a dataset, as >> explained in section "Interpreting datasets" of >> http://www.w3.org/2011/rdf-wg/wiki/TF-Graphs/RDF-Datasets-Proposal. > >> > Oh, wait. We did NOT agree to accept an alien model theory for > datasets. If you wish to propose this, please make it an action item > for the WG. I will argue strongly, and vote, against it. But in any > case, the proposed model theory for datasets, in the proposal, uses > the same language or reference in an interpretation, so does not > resolve the issue I was pointing out. The proposed semantics for datasets does not forbid defining a mechanism to identify graphs. What Pierre-Antoine describes in his email would work, I believe. What is written in "Interpreting datasets" is probably the least constrained form of semantics you can define for a dataset, based on RDF interpretations. It fulfils the need for having diverging opinions expressed in different graphs (or even contradicting graphs) and if some people want more constraining semantics, it's not a problem to extend it. If we don't define the semantics, I'm afraid there's going to be endless discussions or misunderstanding about what the stuff in the dataset entails. >> >> Now, the use cases clearly show that we need a way to identify a >> graph (or rather a g-box) with a URI. My understanding was that >> this is independent from today's decision, and I hope it is. > > Quite. And if it is, then this use of a URI to identify a graph > (g-box, whatever) will be independent of the SPARQL use of URIs to > identify graphs. And hence, my point about the use of URIs in RDF > triples will still stand. I do not see what is the problem of having URIs that identify graphs (in the RDF interpretation sense) together with additional labels for graphs which just happen to be URIs too. :antoine { :g a :Graph . :antoine a :Person } works for me. If I want I can (for my personal purpose, not for the WG) extend the RDF interpretation with an additional "graph-map" which maps URIs to graphs such that a URI can identify a thing (a person, a cow, an idea) as well as a graph. In OWL 2 DL, you have 3 interpretation functions that maps URIs to different things. An individual-interpration, a property-interpretation and a class-interpretation. These three interpretations can map the same URI to 3 distinct things, such that a URI "names" multiple things having a different nature. Names map to things *in a context*. A URI names a thing in RDF by way of its RDF-interpretation but a URI can name a graph in a dataset by way of what is called "named graphs" in the SPARQL spec. I could also name my dog Tim Berners-Lee, or even name it using TimBL's URI and register this identification somehow and that would not be a problem for RDF (although, I agree, it would be silly). AZ. > So all is not good, unless you are in agreement that SPARQL cannot > use the same identifier in an RDF object position and also to > identify a graph in a dataset. > > Pat > >> >> So all is good so far. >> >> >> Le 14/04/2011 19:09, Pat Hayes a écrit : >>> Well, the use of a URI inside an RDF triple assumes that the URI >>> is being used as a name, to refer to something. Using a URI which >>> is the name of a named graph, for example, would refer to the >>> graph. But in this decision we *explicitly* say that this is >>> *not* how the SPARQL association of URIs to graphs works: that >>> the 'associated' graph which is 'tagged' (if I have that right) >>> by a URI might well not be the entity referred to by the URI. The >>> example was given in which the URI is the name of a person, ie >>> refers to a person, and still can be used to 'tag' a graph for >>> SPARQL purposes. If such a URI is used as the object of an RDF >>> triple, it will refer to the person, not to the SPARQL-tagged >>> graph. As there is no way to know whether the graph that is >>> SPARQL-tagged by a URI is, or is not, the referent of the URI, >>> any use of that URI as a name inside an RDF triple must be >>> basically unrelated to its use as a SPARQL graph tag; or at any >>> rate, that is the only safe assumption to make. >>> >>> In a nutshell, RDF uses URIs as referring names. Apparently, >>> SPARQL does not, when it comes to identifying graphs. So the uses >>> of URIs in RDF triples and in SPARQL tags are dissociated from >>> one another, and need have no relationship. So, no relationship >>> can be relied upon. The 'naming' of graphs in SPARQL is a wholly >>> SPARQL-local business, unrelated to RDF semantics and therefore >>> to any RDF content. >>> >>> I assumed this was obvious at the time we were discussing this, >>> by the way. But I confess I had not at that time read the Wiki >>> proposal fully, and not seen the 'imports' examples. >>> >>> Pat >>> >>> On Apr 14, 2011, at 11:55 AM, Ivan Herman wrote: >>> >>>> Pat, >>>> >>>> sorry, but you will have to explain (me) what the problem is. >>>> >>>> Ivan >>>> >>>> ---- Ivan Herman web: http://www.ivan-herman.net mobile: +31 >>>> 64 1044 153 >>>> >>>> On 14 Apr 2011, at 18:43, Pat Hayes<phayes@ihmc.us> wrote: >>>> >>>>> I note in passing that the Proposed WG Decision dated 14 >>>>> April has the consequence that the IRi associated with a >>>>> graph in SPARQL cannot be used inside an RDF triple to >>>>> reliably refer to the graph. This means in particular that >>>>> uses such as those contemplated in >>>>> http://www.w3.org/2011/rdf-wg/wiki/TF-Graphs/RDF-Datasets-Proposal, >>>>> >>>>> which use the SPARQL name as the object in an 'imports' triple, >>>>> are ruled out by this decision. >>>>> >>>>> Pat >>>>> >>>>> On Apr 13, 2011, at 4:29 AM, RDF Working Group Issue Tracker >>>>> wrote: >>>>> >>>>>> >>>>>> ISSUE-30: How does SPARQL's notion of RDF dataset relate >>>>>> our notion of multiple graphs? >>>>>> >>>>>> http://www.w3.org/2011/rdf-wg/track/issues/30 >>>>>> >>>>>> Raised by: On product: >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> >>>>> >>>>> ------------------------------------------------------------ >>>>> IHMC (850)434 8903 or (650)494 3973 40 South Alcaniz St. >>>>> (850)202 4416 office Pensacola (850)202 4440 fax FL >>>>> 32502 (850)291 0667 mobile phayesAT-SIGNihmc.us >>>>> http://www.ihmc.us/users/phayes >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>> >>> >>> ------------------------------------------------------------ >>> IHMC (850)434 8903 or (650)494 3973 40 South Alcaniz St. (850)202 >>> 4416 office Pensacola (850)202 4440 >>> fax FL 32502 (850)291 0667 mobile >>> phayesAT-SIGNihmc.us http://www.ihmc.us/users/phayes >>> >>> >>> >>> >>> >>> >> >> > > ------------------------------------------------------------ IHMC > (850)434 8903 or (650)494 3973 40 South Alcaniz St. > (850)202 4416 office Pensacola (850)202 > 4440 fax FL 32502 (850)291 0667 > mobile phayesAT-SIGNihmc.us http://www.ihmc.us/users/phayes > > > > > -- Antoine Zimmermann Researcher at: Laboratoire d'InfoRmatique en Image et Systèmes d'information Database Group 7 Avenue Jean Capelle 69621 Villeurbanne Cedex France Tel: +33(0)4 72 43 61 74 - Fax: +33(0)4 72 43 87 13 Lecturer at: Institut National des Sciences Appliquées de Lyon 20 Avenue Albert Einstein 69621 Villeurbanne Cedex France antoine.zimmermann@insa-lyon.fr http://zimmer.aprilfoolsreview.com/
Received on Friday, 15 April 2011 09:18:50 UTC