document: Topical query decomposition We introduce the problem of query decomposition , where we are given a query and a document retrieval system , and we want to produce a small set of queries whose union of resulting documents corresponds approximately to that of the original query . Ideally , these queries should represent coherent , conceptually well-separated topics . We provide an abstract formulation of the query decomposition problem , and we tackle it from two different perspectives . We first show how the problem can be instantiated as a specific variant of a set cover problem , for which we provide an efficient greedy algorithm . Next , we show how the same problem can be seen as a constrained clustering problem , with a very particular kind of constraint , i.e. , clustering with predefined clusters . We develop a two-phase algorithm based on hierarchical agglomerative clustering followed by dynamic programming . Our experiments , conducted on a set of actual queries in a Web scale search engine , confirm the effectiveness of the proposed solutions .
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