11. The system of claim 9 , wherein the operations further comprise: generating an expansion/contraction table that includes pairs of sequences of terms having highest respective similarity measures; and identifying a plurality of pairs of sequences of terms that include the first sequence of terms in the expansion/contraction table.
11. The system of claim 9 , wherein the operations further comprise: generating an expansion/contraction table that includes pairs of sequences of terms having highest respective similarity measures; and identifying a plurality of pairs of sequences of terms that include the first sequence of terms in the expansion/contraction table. 12. The system of claim 11 , wherein generating the expansion/contraction table comprises: determining a plurality of frequently occurring word sequences; and filtering out non-phrasal word sequences from the frequently occurring word sequences, wherein a non-phrasal word sequence is a word sequence that does not occur at a beginning or an end of at least a threshold number of queries in a collection of queries.