I have encountered a problem with federating Wikidata entities with LOD based on the abundant external resource "literal identifiers" that are represented in Wikidata. An external resource identifier should include the entire IRI to the resource, not just the "id", otherwise the external resource cannot be federated in a SPARQL query without concatenating the IRI to the literal identifier and binding to a new variable.
The triple pattern fragment implementation that I am working with does not allow bind grouping in the sparql query, so this unfortunately makes federation of Wikidata entities by Identifiers nearly impossible. Hence, the only federation that I have been able to do effectively is "to" Wikidata not "from" it....
If anyone is interested, I have setup Wikidata as a TPF datasource here: