One of the big added value of Wikidata imho is that each Wikidata page mention the identifiers for the same item in several other datasets (OSM, wikipedia, geon

One of the big added value of Wikidata imho is that each Wikidata page mention the identifiers for the same item in several other datasets (OSM, wikipedia, geonames, etc). Given the fact that SPARQL allows cross-DB queries, Wikipedia becomes an interesting federation dataset.