Martynas,
what you are proposing below is not W3C recommended RDF but an extension of triples to quads. As far as I know, this extension is not compatible yet with existing standards such as SPARQL and OWL. Named graphs work with SPARQL, but are mostly used in another way than you suggest. Most RDF database tools would be *very* unhappy to get millions of named graphs in combination with queries that use variables as graph names. The syntax you use is not a W3C standard either.
This does not say that N-Quads aren't a good idea if one can get them to work with the rest of the Semantic Web stack, but it really defeats your own arguments. We are committed to supporting *existing* standards (as we have said many times already), but we will not base our software design on a non-standard RDF-variant that works with neither OWL nor SPARQL.
Markus
On 06/04/12 13:09, Martynas Jusevicius wrote:
Hey Denny,
I gave it a shot:
http://dbpedia.org/resource/France http://dbpedia.org/ontology/PopulatedPlace/populationDensity "116"^^http://dbpedia.org/datatype/inhabitantsPerSquareKilometre http://wikidata.org/graphs/France2012 . http://dbpedia.org/resource/France http://dbpedia.org/ontology/populationDensity "116"^^http://www.w3.org/2001/XMLSchema#double http://wikidata.org/graphs/France2012 .
http://wikidata.org/graphs/France2012 http://purl.org/dc/terms/date "2012"^^http://www.w3.org/2001/XMLSchema#year http://wikidata.org/graphs/France2012 . http://wikidata.org/graphs/France2012 http://purl.org/dc/terms/source _:source http://wikidata.org/graphs/France2012 . _:sourcehttp://purl.org/dc/terms/published "2010"^^http://www.w3.org/2001/XMLSchema#year http://wikidata.org/graphs/France2012 . _:sourcehttp://purl.org/dc/terms/title "Bilan demographique"@fr http://wikidata.org/graphs/France2012 .
The syntax is N-Quads. It does not use reification, but instead named graphs for provenance. The necessary concepts were already present in DBPedia.
As you might know, temporal provenance is not the strongest point of RDF. However conventions and solutions are available, and I am sure implementing them would require far less effort than creating a custom data model from scratch, not to mention the benefits of potential reuse. There's quite some research done on RDF provenance, which is worth looking into if provenance is really a key feature for Wikidata from day one. I see it as something that should work transparently behind the scenes, and therefore could be rolled-out later on.
You would get much better and more extensive advice than mine on semantic-web@w3.org -- the only prerequisite is willingness to cooperate.
RDF's strength is that it solves data integration problems by pivotal conversion, reducing the number of model transformations from quadratic to linear: http://en.wikipedia.org/wiki/Data_conversion#Pivotal_conversion A custom data model brings up questions which already have an answer in the Semantic Web stack: # can data from different Wikidata instances be merged or interlinked natively? # is there a native query language? In case of SQL, how performant will it be given many JOINs and the planned use of provenance? # what and how many custom serialization formats and API mechanisms will have to follow?
Stacking one custom solution on top of another can eventually result in huge costs. I honestly think the energy of Wikidata could be directed in a more productive way.
Martynas graphity.org
2012/4/5 Denny Vrandečićdenny.vrandecic@wikimedia.de:
Dear Martynas,
if you try to model the following statement in RDF
"The population density of France, as of an 2012 estimate, is 116 per square kilometer, according to the "Bilan demographique 2010"."
you might notice that RDF requires a reification of the statement. The data model that you have seen provides us with an abstract and concise way to talk about these reifications (i.e. via the statement model, just as in RDF).
We still have not finished the document describing how to map our data model to OWL/RDF, but we have thought about this the whole time while discussing the data model.
But if you find a simpler, and more RDFish way to express the above statement, please feel free to enlighten me. I would be indeed very interested.
Cheers, Denny
2012/4/5 Martynas Juseviciusmartynas@graphity.org
it doesn't look like reuse of existing concepts and standards is a priority for this project. One cannot build a Semantic Web application by ignoring its main building block, which is the RDF data model.
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