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> .
_:source<http://purl.org/dc/terms/published>
"2010"^^<http://www.w3.org/2001/XMLSchema#year>
<http://wikidata.org/graphs/France2012> .
_:source<http://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-...@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 Vrandečić<denny.vrande...@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 Jusevicius<marty...@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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