12. The method of claim 11 , wherein boosting the ranking score for the matching query completion comprises computing a new ranking score for the matching query completion based on multiplying an initial ranking score for the matching query completion by a boost value B, wherein B is based on the likelihood score associated with the first likely query.
12. The method of claim 11 , wherein boosting the ranking score for the matching query completion comprises computing a new ranking score for the matching query completion based on multiplying an initial ranking score for the matching query completion by a boost value B, wherein B is based on the likelihood score associated with the first likely query. 13. The method of claim 12 , wherein the boost value B is given by: B = P ⁡ ( x ❘ q ) P ⁡ ( x ) , wherein P(x|q) is a measure of the likelihood of the matching query completion x occurring in an activity session given that a the reference query q also occurred in the same activity session, and P(x) is a measure of the likelihood of the query completion x appearing in an activity session.