9. A computer-readable medium encoded with instructions for controlling a computing device to determine frequency of a query at an interval, by a method comprising: storing frequencies of the query during intervals; generating autoregressive integrated moving average (“ARIMA”) coefficients representing the query based on the stored frequencies; estimating the frequency of the query at the interval based on the ARIMA coefficients for the query; and determining similarity between a pair of queries based on the ARIMA coefficients for the queries, the determining including aggregating products, for each ARIMA coefficient, of a first factor of a first query of the pair and a second factor of a second query of the pair, a factor for an ARIMA coefficient of a query being a difference between the ARIMA coefficient and a mean of the ARIMA coefficients divided by a standard deviation of the ARIMA coefficients.
10. The computer-readable medium of claim 9 wherein the estimated frequency is a predicted frequency for a future interval.