Hi Claus,
a brief partial reply:
On 13/08/13 16:20, Claus Stadler wrote: ...
For example, I notice that the Wikidata page for my home town "Berndorf in Lower Austria" does not contain the population: http://www.wikidata.org/wiki/Q666615
This is because the Wikidata datatype for numbers is not implemented yet.
Looking at the corresponding DBpedia entry, this information actually exists there: http://dbpedia.org/resource/Berndorf,_Lower_Austria
The new DBpedia interface should offer a button next to the "population 8728" triple which enables transfer of this information to Wikidata.
To edit Wikidata, you should create an account. If you intend to do mass edits, this account should be granted bot status first to avoid it from being blocked if it sends a lot of requests. This is mostly a community process: you should discuss the intended edit activities with the community to find out if they are happy with this (this list is only about the technical aspects). It is good to have additional inputs, but I could imagine that most of the data gets bulk imported from Wikipedia infoboxes by the community anyway, which is what happens with a lot of data right now.
In another GSoC project, Hady Elsahar is working on mappings between the wikidata RDF vocabulary and the DBpedia vocabulary. This means, we can in principle map DBpedia RDF data to Wikidata RDF.
Note that there are some differences beyond the vocabulary. Most Wikidata statements have source information attached, and there are also qualifiers (not used heavily yet, since the selection/filtering mechanisms of Wikidata are quite weak so far, but this will change). In some domains, such as roles of actors in films, quantifiers are getting widely used now; so this is not really triple data any more. But there will be enough triple data left, I guess.
However, looking at the Wikidata API [2] there is
action=wbcreateclaim * with the example:
api.php?action=wbcreateclaim&entity=q42&property=p9001&snaktype=novalue&token=foobar&baserevid=7201010
So the core question is, how can we map e.g. properties such as wikidata:population (if that existed) to their respective Wikidata property identifier (Q12345)? This goes for any property that may occur in an RDF dump, such as: http://www.wikidata.org/wiki/Special:EntityData/Q666615.nt
Note that all property ids start with a P. If it's of the form Q..., then it is not a property.
Cheers,
Markus