11. A computer storage medium encoded with a computer program, the program comprising instructions that when executed by a data processing apparatus cause the data processing apparatus to perform operations comprising: ranking indexed queries based on a query rank of each indexed query, the query rank calculated based on a frequency of occurrence of the indexed query and a user satisfaction score of the indexed query, the indexed queries including highly-ranked queries that are a predetermined number of queries selected based on the query rank, and nearby queries that are queries that have a statistically significant probability of being revised to one of the highly-ranked queries; calculating a respective revision score for each indexed query as a function of a revision probability of the first query and the query rank for the indexed query, the revision probability based on at least one of a semantic similarity and syntactic similarity between the first query and the respective indexed query; selecting one of the indexed queries as an alternative query to the first query based on the revision score; determining whether the alternative query is one of the highly-ranked queries or whether the alternative query is one of the nearby queries; if the alternative query is one of the highly-ranked queries, providing the highly-ranked query as a suggested revision for the first query; and if the alternative query is one of the nearby queries, providing a highly ranked query that the nearby query has a statistically significant probability of being revised to, as the suggested revision for the first query.
11. A computer storage medium encoded with a computer program, the program comprising instructions that when executed by a data processing apparatus cause the data processing apparatus to perform operations comprising: ranking indexed queries based on a query rank of each indexed query, the query rank calculated based on a frequency of occurrence of the indexed query and a user satisfaction score of the indexed query, the indexed queries including highly-ranked queries that are a predetermined number of queries selected based on the query rank, and nearby queries that are queries that have a statistically significant probability of being revised to one of the highly-ranked queries; calculating a respective revision score for each indexed query as a function of a revision probability of the first query and the query rank for the indexed query, the revision probability based on at least one of a semantic similarity and syntactic similarity between the first query and the respective indexed query; selecting one of the indexed queries as an alternative query to the first query based on the revision score; determining whether the alternative query is one of the highly-ranked queries or whether the alternative query is one of the nearby queries; if the alternative query is one of the highly-ranked queries, providing the highly-ranked query as a suggested revision for the first query; and if the alternative query is one of the nearby queries, providing a highly ranked query that the nearby query has a statistically significant probability of being revised to, as the suggested revision for the first query. 15. The computer storage medium of claim 11 , wherein the alternative query is the highly-ranked query.