1. A computer-implemented method, comprising: scoring an alteration candidate for a query, the alteration candidate comprising multiple alteration terms, the query comprising multiple query terms, and the scoring comprising: computing one or more query-dependent feature scores that are based on dependencies to multiple query terms from each of one or more of the alteration terms; computing one or more intra-candidate-dependent feature scores that are based on dependencies between different terms in the alteration candidate; and computing a candidate score for the candidate using the one or more query-dependent feature scores and the one or more intra-candidate-dependent feature scores; and determining whether to select the candidate to expand the query, the determination using the candidate score.