1. A method comprising: obtaining access, by at least one computer processor, to a relationship network; obtaining access, by said at least one computer processor, to a network of a different kind than said relationship network; obtaining, by said at least one computer processor, a user query; and carrying out a multiple heterogeneous networks search on said relationship network and said network of said different kind than said relationship network, by executing on said at least one computer processor a multiple heterogeneous network search module, to obtain a ranked output list responsive to said user query.