17. The system of claim 12 , wherein the operations further comprise: determining a query value Q for the query, the query value being based on the QtoA ratio; determining a resource value D for the resource, the resource value being based on a function of an age of the resource, F(age), wherein age is the age of the resource; and calculating S′ as a product of S and a value of a boosting function of the query value Q and the resource value D.
19. The system of claim 17 , wherein the boosting function has the form f (Q, D)=Q D .