39. The method of claim 30 , wherein the query has one or more query blocks and wherein determining the set of candidate queries comprises determining a particular semantically equivalent query based on the query and an alternative query block, wherein the alternative query block is determined based on a first query block of the one or more query blocks.
39. The method of claim 30 , wherein the query has one or more query blocks and wherein determining the set of candidate queries comprises determining a particular semantically equivalent query based on the query and an alternative query block, wherein the alternative query block is determined based on a first query block of the one or more query blocks. 40. The method of claim 39 , wherein the method further comprises the step of determining the alternative query block based on the first query block.