1. A method comprising: receiving at a server a plurality of values for a plurality of controls of an interactive form, each value comprising a portion of a travel-related search query entered into one of the controls of the interactive form by each of a plurality of users; determining with the server a plurality of recommendation rules based upon the values for interrelated controls, each recommendation rule logically connecting two or more of the interrelated controls; computing the plurality of recommendation rules using collaborative historical data in a history database; and aggregating at least one data set within the collaborative historical data in the history database according to increasing coarse granularity if a size of the data set is below a threshold, wherein aggregation of the at least one data set based on the increasing coarse granularity improves a statistical significance of the plurality of recommendation rules.