7. A computer-implemented method comprising: receiving a query in a user session, the query comprising one or more search parameters; detecting, in the user session and after receiving the query, a user event associated with an item in search results for the query; determining a property associated with the item in the search results; creating a refinement comprising an association between the property and the one or more search parameters, wherein refinements record hierarchical associations between properties of items and a corresponding one or more search parameters, and wherein the association between the property and the one or more search parameters is associated with a score that is updated based on a plurality of user actions, wherein the score is updated based on changing the score; and ranking search results for a subsequent query based on a plurality of refinements comprising the refinement.
11. The method of claim 7 , wherein scores in a plurality of refinements comprising the refinement are represented as percentages such that the search results are selected in similar percentages.