2. The computer-implemented method of claim 1 , wherein obtaining the at least one concept semantically relevant to the first search query comprises: constructing a merged semantic network based on the reference semantic network and the target semantic network; identifying or generating a first concept in the merged semantic network, the first concept representing the user-specified search query; obtaining the at least one concept, including a second concept, semantically relevant to the first concept at least in part by synthesizing the second concept based on the first concept and at least one other concept in the merged semantic network.
7. The computer-implemented method of claim 2 , wherein obtaining the at least one concept comprises: obtaining a plurality of concepts semantically relevant to the first concept; computing a score for one or more concepts in the plurality of concepts, wherein the score for a specific concept is indicative of the semantic relevance of the specific concept to the first concept; and selecting the at least one concept based on the scores computed for the one or more concepts.