- From: Antoine Zimmermann <antoine.zimmermann@insa-lyon.fr>
- Date: Fri, 02 Sep 2011 13:21:26 +0000
- To: public-rdf-wg@w3.org
Pierre-Antoine Champin <pierre-antoine.champin@liris.cnrs.fr> a écrit : > On 08/27/2011 06:39 PM, Richard Cyganiak wrote: >> On 27 Aug 2011, at 06:39, Ivan Herman wrote: >>> http://www.w3.org/2009/07/NamedGraph.html >> >> You could have told us about that earlier Ivan! > > Indeed! :) > >> /me prints a copy > > same here... > > A quick look at this document helped me realize something (that I should > have realized earlier, when Richard suggested that I used datatyped > literals): > > using datatyped literals, rather than "plain" strings, to describe graph > literals, has a very nice feature: it puts the concrete syntax (used to > described the graph) back where it belongs: outside of the abstract syntax. > > Take the following example: > > 1 <#pa> :believes """ > 2 @prefix : <some-uri#> . > 3 :graph-literals :are :easy. > 4 """^^rdfl:graphLiteral . > > The abstract syntax of the turtle above knows nothing of lines 2-3. In > fact, I could have written: > > 1 <#pa> :believes """ > 2 @prefix foo: <some-uri#> . > 3 @prefix bar: <some-uri#> . > 4 foo:graph-literals > 5 <some-uri#are> > 6 bar:easy > 7 . > 8 """^^rdfl:graphLiteral . > > and that would be (from the abstract syntax POV) *exactly* the same > graph, just like > > :a :b "00000001"^^xsd:integer . > > and > > :a :b 1 . > > are exactly the same triple. In fact, no. The two triples are equivalent (that is, they entail each other) but they are distinct. To be precise, the two triples are equivalent under D-entailment, otherwise they are not even entailing one another. > > That being said, I hear Antoine's arguments that this is out of the > scope of the group, and should rather be explored as a research work. > I'm still open for both options. > > pa > >> >> Best, >> Richard >> >> >> >>> >>> On Aug 26, 2011, at 18:39 , Antoine Zimmermann wrote: >>> >>>> Pierre-Antoine, >>>> >>>> >>>> I am in total agreement with what Richard says below. However, I sympathise to some extent with your idea. I would be interested to see some people define a datatype for serialised graphs, say in Turtle. Then, they should brainstorm a few use cases and implement some tools around this proposal and see how things are going, gather experiences and come back in a few year with a report and possibly a proposal for standardisation. >>>> >>>> Start by defining a datatype for Turtle graph literals: >>>> - lexical space is the set of valid Turtle documents; >>>> - value space is the set of RDF graphs; >>>> - L2V is the mapping from Turtle to RDF graph, as defined in th Turtle spec. >>>> >>>> Of course, you can do the same for other syntaxes, but I think Turtle best fits. >>>> >>>> Then you may need to introduce a set of terms like rdf:Graph, rdf:serialisation, etc... This set of terms should be crafted in function of the experience that the group gather by trying to deal with their use cases. >>>> >>>> BUT, this is certainly not something that should be done within this working group. >>>> >>> >>> A few years ago I had an attempt to do something like that >>> >>> http://www.w3.org/2009/07/NamedGraph.html >>> >>> but then, somehow, I did not _really_ finish it and I am sure it is full of rubbish, too, mainly on the semantics side. But my basic approach in terms of the serialization of this stuff was much more restrictive than Pierre-Antoine's, namely that within a specific serialization one can use only the same serialization for a graph. I indeed do not see why one would allow to use, say, RDF/XML to encode a graph literal when one is in Turtle... >>> >>> Although the document is there, I am _not_ sure this is something this WG has to really take up. This is still open in my mind. >>> >>> Ivan >>> >>>> >>>> AZ. >>>> >>>> Le 22/08/2011 18:54, Richard Cyganiak a écrit : >>>>> Pierre-Antoine, >>>>> >>>>> Thanks for picking this up again. >>>>> >>>>> There are several things I don't like about [2]. >>>>> >>>>> 1. It is not an abstract syntax. It is a mix of concrete and abstract >>>>> syntax. Thus it negates the benefits of having an abstract syntax in >>>>> the first place. For example, one cannot really describe any >>>>> operations over such a multigraph representation without appealing to >>>>> the use of various syntax parsers. And one has to explain what >>>>> happens if the serialized graph isn't valid in the respective syntax. >>>>> Etc >>>>> >>>>> 2. It doesn't achieve the goal of standardisation. Different existing >>>>> multigraph approaches (TriG, SPARQL, etc) would all look differently >>>>> when expressed according to this proposal. Thus, it doesn't promote >>>>> interoperability and doesn't actually make working with multiple >>>>> graphs any easier. >>>>> >>>>> 3. I feel that it is actually more complex than the RDF Dataset >>>>> proposal [1] because it requires the definition of one predicate for >>>>> every RDF graph serialization, as well as additional vocabulary for >>>>> every multigraph representation. >>>>> >>>>> 4. It is clear that actually storing or serializing anything in that >>>>> way would be a bad idea. Instead, one wants to use optimized syntaxes >>>>> that can serialize the graph literals without ?double serialization?, >>>>> and optimized storage schemes that can actually store and index the >>>>> parsed form of the graph literals. But if that is the case, then why >>>>> not define an abstract syntax that actually reflects these concrete >>>>> syntaxes and storage schemes? >>>>> >>>>> 5. From a pure RDF modeling and semantics point of view, this >>>>> proposal should use typed literals and not plain/xsd:string >>>>> literals. >>>>> >>>>> Best, Richard >>>>> >>>>> >>>>> On 22 Aug 2011, at 16:12, Pierre-Antoine Champin wrote: >>>>> >>>>>> As I promissed to Richard during the last TC, I'm reactivating the >>>>>> thread on his proposal to "lift" the definition of RDF datasets >>>>>> into from SPARQL to RDF concepts [1] >>>>>> >>>>>> My main concern with this proposal is that it defines a somewhat >>>>>> complex structure (the dataset) as a primitive concept in RDF. My >>>>>> gut feeling is that we could instead define more basic concepts, on >>>>>> top of which SPARQL datasets, SPARQL graph stores, and possibly >>>>>> other structures, could be defined. In my understanding, this is >>>>>> what the g-* terminology was aiming at. >>>>>> >>>>>> In this perspective, back in June, I made an alternate proposal [2] >>>>>> for which I got almost no feedback. In a nutshell, it provides a >>>>>> minimal vocabulary for reifying RDF graphs into standard RDF, and >>>>>> sketches the semantics of such a reification. From there, it >>>>>> illustrates how multi-graphs syntaxes (such as Trig) and models >>>>>> (such as SPARQL datasets) can be defined on top of it. >>>>>> >>>>>> I know that Richard was concerned about several multi-graph models >>>>>> had slight differences (e.g. can a BNode be used as a graph name), >>>>>> and his solution was to endorse one of them and wait for the others >>>>>> to converge. My proposal is rather to provide the building blocks >>>>>> for everyone to describe their model in RDF itself, and leave it >>>>>> open for different models to coexist, which is ok as long as they >>>>>> can all be expressed in plain RDF. >>>>>> >>>>>> pa >>>>>> >>>>>> >>>>>> [1] >>>>>> http://www.w3.org/2011/rdf-wg/wiki/TF-Graphs/RDF-Datasets-Proposal >>>>>> [2] >>>>>> http://www.w3.org/2011/rdf-wg/wiki/TF-Graphs/RDF-Quadless-Proposal >>>>> >>>>> >>>> >>>> >>>> -- >>>> 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/ >>>> >>> >>> >>> ---- >>> Ivan Herman, W3C Semantic Web Activity Lead >>> Home: http://www.w3.org/People/Ivan/ >>> mobile: +31-641044153 >>> PGP Key: http://www.ivan-herman.net/pgpkey.html >>> FOAF: http://www.ivan-herman.net/foaf.rdf >>> >>> >>> >>> >>> >>> >> >> >> > > >
Received on Wednesday, 7 September 2011 08:48:29 UTC