Dear Martynas,

I understand your concern. Markus already commented on the Quads and the fact that there are no where used in the way you suggest it. I am thankful for critically accompanying our design phase, but I would again ask you for some patience until we have the RDF mapping drafted.

We are very well aware of the advantages and importance of using Semantic Web standards. And I know well what a Semantic Web application is. Heck, check my CV. I've been two times finalist for the Semantic Web Challenge. And I know many people involved in the provenance working group, as well as those who have been working on standards like RDF and OWL. So even though this doesn't mean much -- people should be judged by their actions, not by their pedigree or social network -- I at least hope that you will be able to wait until we drafted our RDF mapping document. I would hope that, as soon as we do that, you will again critically review our work.

Cheers,
Denny


2012/4/6 Martynas Jusevicius <martynas@graphity.org>
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-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 Vrandečić <denny.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 Jusevicius <martynas@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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Wikimedia Deutschland - Gesellschaft zur Förderung Freien Wissens e.V. Eingetragen im Vereinsregister des Amtsgerichts Berlin-Charlottenburg unter der Nummer 23855 B. Als gemeinnützig anerkannt durch das Finanzamt für Körperschaften I Berlin, Steuernummer 27/681/51985.