FYI in SPARQL

  SELECT ?foaf
  WHERE 
  {
    ?me a <USER> .
    ?me <KNOWS> ?friend . ?friend <KNOWS> ?foaf .
    MINUS {:me <KNOWS> ?foaf }
  }

OR

  SELECT ?foaf
  WHERE 
  {
    ?me a <USER> .
    ?me <KNOWS>/<KNOWS> ?foaf .
    MINUS {:me <KNOWS> ?foaf }
  }