8. A computer system comprising: at least one processor; and a memory comprising instructions stored thereon that when executed by the at least one processor cause the at least one processor to perform acts 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 intra-candidate dependent feature scores that are based on dependencies between different terms in the alteration candidate, the intra-candidate dependent feature scores comprising at least one skip bigram score; and using the one or more intra-candidate dependent feature scores to compute a candidate score for the candidate; and determining whether to select the candidate to expand the query, the determination using the candidate score.
8. A computer system comprising: at least one processor; and a memory comprising instructions stored thereon that when executed by the at least one processor cause the at least one processor to perform acts 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 intra-candidate dependent feature scores that are based on dependencies between different terms in the alteration candidate, the intra-candidate dependent feature scores comprising at least one skip bigram score; and using the one or more intra-candidate dependent feature scores to compute a candidate score for the candidate; and determining whether to select the candidate to expand the query, the determination using the candidate score. 10. The computer system of claim 8 , wherein the one or more intra-candidate dependent feature scores are based on dependencies between all the terms in the alteration candidate.