DBpedia is an extract of structured information from wikipedia. The structured data can be retrieved using an SQL-like query language for RDF called SPARQL. There is already an R package for this kind of queries named SPARQL.

There is an S4 class Dbpedia part of my datamart package that aims to support the creation of predefined parameterized queries. Here is an example that retrieves data on German Federal States:

> library(datamart)
> dbp <- dbpedia()
> # see a list of predefined queries
> queries(dbp)
Dbpedia#Nuts1 Xsparql#character 
"Nuts1"       "character" 
> # lists Federal States
> head(query(dbp, "Nuts1"))
name nuts    popDate      pop
1           Niedersachsen  DE9 2007-10-31  7977000
2                  Hessen  DE7 2007-09-30  6073000
3     Nordrhein-Westfalen  DEA 2009-01-31 17920000
4 Freie Hansestadt Bremen  DE5 2007-10-31   664000
5                  Berlin  DE3 2010-09-30  3450889
6             Brandenburg  DE4 2008-12-31  2522493
area   gdp popMetro
1 47624200000   188       NA
2 21100000000   225       NA
3 34084100000 54107       NA
4   408000000    24       NA
5   891850000    95  4429847
6 29478600000    48       NA

It is straightforward to extend the Dbpedia class for further queries. More challenging in my opinion is to figure out useful queries. Some examples can be found at Bob DuCharme’s blog, in the article by Jos van den Oever at kde.org, in a discussion on a mailing list and a tutorial at the W3C, at Kingsley Idehen’s blog and at DBpedia’s wiki.