119. The machine-readable storage medium of claim 118 , wherein the one or more sequences of instructions further comprise instructions which, when executed by the one or more processors, cause the one or more processors to perform the step of determining the alternative query block based on the first query block.
118. The machine-readable storage medium of claim 108 , wherein the query has one or more query blocks and wherein the instructions that cause determining the set of candidate queries for each starting query comprise instructions which, when executed by the one or more processors, cause the one or more processors to perform the step of determining a particular semantically equivalent query based on the starting 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.