1. A method of merging search results, comprising: identifying a query from a user; splitting the query into sub-queries; calculating information content for each of the sub-queries, said information content representing information requirements of the user; executing each of the sub-queries to obtain a plurality of search results; and combining the search results based on the information content calculated for the sub-queries; wherein: the executing each of the sub-queries includes identifying a multitude of entities for at least one of the sub-queries, and executing each of the sub-queries in a respective one of a plurality of heterogeneous indices; said sub-queries include a first sub-query and a second sub-query; the executing each of the sub-queries includes executing the first sub-query to identify a plurality of first class entities, and executing the second sub-query to identify a multitude of second class entities, each of the second class entities being associated, according to a defined criteria, with a respective single first class entity; the combining includes clustering the second class entities into a plurality of clusters based on the first class entity to which each of the second class entities belongs, and assigning a relevance score to each of the clusters; the combining includes determining an importance value for each of the first class entities; and the assigning includes assigning a relevance score to each of the clusters based on the importance value of the first class entity with which the second class entities of said each cluster are associated.