- From: Andy Seaborne <andy.seaborne@epimorphics.com>
- Date: Tue, 19 Feb 2013 15:10:32 +0000
- To: Pat Hayes <phayes@ihmc.us>
- CC: Markus Lanthaler <markus.lanthaler@gmx.net>, public-linked-json@w3.org, 'RDF-WG' <public-rdf-wg@w3.org>
On 19/02/13 04:27, Pat Hayes wrote: > > On Feb 18, 2013, at 1:13 PM, Andy Seaborne wrote: > >> >> >> On 18/02/13 18:19, Markus Lanthaler wrote: >>> On Monday, February 18, 2013 7:01 PM, Andy Seaborne wrote: >>>> You, JSON-LD, can add the constraint that a bNode/IRI is >>>> actually referring to the graph. >>> >>> if that's not standardized across all RDF dataset syntaxes you >>> couldn't transform the JSON-LD data to another syntax. >> >> Hence my suggestion for using IRIs minted by the parser because you >> can define them to denote the graph. > > How do you do this, Andy? The IRI being minted is under the control of the JSON-LD spec - it gets to define its meaning. > How is this act of definition recorded? I suggest in the default graph. But Manu suggests that being under control of JSON-LD is enough. > If > I read a dataset somewhere on the Web and it has IRIs in it, how > would I know that they had been "defined" in this way so that I knew > they were intended to denote a graph? Either know the provenance of the data or look at the URI pattern and know it's JSON-LD generated. > All I have is the dataset > (perhaps in the form of a document which parses to the dataset) and > the RDF specifications: and the latter tell me that I *cannot* make > this assumption. > >> You can then define the output of JSON-LD parsing that a graph >> label using one of these IRIs is denoting the graph. owl:sameAs >> (except that's for "individuals" > > Only in OWL-DL. Use Owl-Full and you are OK. :-) > >> / "IRI"). >> >>>> (but then the graph is an abstract value - not the JSON-LD >>>> normalized structure, Turtle document or any specific bytes. >>>> 1, 01, +1 and all that). >>> >>> Yes, I was always talking about the abstract construct and not >>> the bits and bytes on the wire. >>> >>> >>>>> 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? >>>> >>>> If you say they do, they do. Ditto IRIs. >>> >>> You mean the JSON-LD specification would have to say that? >>> >>> >>>>> RDF-CONCEPTS says: >>>>> >>>>> Despite the use of the word "name" in "named graph", the >>>>> graph name does not formally denote the graph. It is merely >>>>> syntactically paired with the graph. RDF does not place any >>>>> formal restrictions on what resource the graph name may >>>>> denote, nor on the relationship between that resource and >>>>> the graph. >>>>> >>>>> I read this as in the example above you wouldn't know to what >>>>> the >>>> signature >>>>> applies. It may or may not be the graph. Manu's use case >>>>> requires >>>> that it is >>>>>> >>> >> the graph to which the signature applies. That's the reason why I >>>> argued for >>>>> "bNodes MUST denote the graph". >>>> >>>> You can add that as a requirement for JSON-LD (and that's true >>>> for bNodes or IRIs) - there is no need to make RDF adopt one >>>> position or the other, excluding the common current usages that >>>> we enumerated over the long discussions. >>> >>> Really? Could you then still round-trip the data between >>> different syntaxes without changing its semantics? >> >> Yes, round trip from JSON-LD-X -> TriG or NQuads -> JSON-LD, (where >> JSON-LD-X is the restriction of JSON-LD to RDF+Datasets - no Bnode >> or literal properties, etc) It's just transcoding of the abstract >> data model and is neutral to semantics in graph labelling or IRI >> minting. > > But the question arises, since this is 'neutral to semantics', > whether the Trig/NQuads has the same meaning as the JSON-LD had. I > think right now it does not. > So the reverse mapping must be doing > something that does not preserve meaning. So, although I don't follow > the fine details, but I will bet you a good steak dinner that there > will be some case where RDF-valid processing in the middle will break > the reverse mapping to JSON-LD. Markus was asking about a round-trip between syntaxes of a dataset, not the more general changing the dataset en route. Andy > > Pat > >> >> Andy >> >>> >>> >>> >>> -- Markus Lanthaler @markuslanthaler >>> >> >> > > ------------------------------------------------------------ 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 > > > > >
Received on Tuesday, 19 February 2013 15:11:12 UTC