Thanks, @jeswr an apology for replying so late.
Comunica is a great SPARQL federated query engine.
But what I’m looking for is application websites that are based on these federated query engines, so are these federated query engines being used well?
Websites like http://linkedlifedata.com/ that I have read so far do not actually use SPARQL federated query technology,
but localize the data and use a uniform IRI prefix to store different datasets as a named graph.