1. A method for providing query suggestions for a user comprising: receiving a query log of client machine sessions on a publication system, at least one session comprising a plurality of queries, query transitions and a purchase-related event; generating by at least one computer processor transition scores comprising scores for ordered pairs of the plurality of queries based on transition from a query of an ordered pair to the purchase-related event; building a set of query suggestions from the transition scores by a score accumulation process; computing similarity scores for the set of query suggestions to determine whether a similarity score for at least one member of the set of query suggestions meets a threshold; and providing to a client machine a list of query suggestions including query suggestions that meet the threshold.