- From: Richard Cyganiak <richard@cyganiak.de>
- Date: Sat, 27 Aug 2011 17:39:10 +0100
- To: Ivan Herman <ivan@w3.org>
- Cc: antoine.zimmermann@insa-lyon.fr, public-rdf-wg@w3.org
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! /me prints a copy 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 Saturday, 27 August 2011 16:41:49 UTC