  The class of queries for detecting path is an important as those can extract
implicit binary relations over the nodes of input graphs. Most of the path
querying languages used by the RDF community, like property paths in W3C SPARQL
1.1 and nested regular expressions in nSPARQL are based on the regular
expressions. Federated queries allow for combining graph patterns and
relational database that enables the evaluations over several heterogeneous
data resources within a single query. Federated queries in W3C SPARQL 1.1
currently evaluated over different SPARQL endpoints. In this paper, we present
a federated path querying language as an extension of regular path querying
language for supporting RDF graph integration with relational database. The
federated path querying language is absolutely more expressive than nested
regular expressions and negation-free property paths. Its additional
expressivity can be used for capturing the conjunction and federation of nested
regular path queries. Despite the increase in expressivity, we also show that
federated path queries are still enjoy a low computational complexity and can
be evaluated efficiently.
