Abstract:

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.