A data processing apparatus is provided that includes forecast circuitry for generating a forecast of an aspect of a system for a next future time and for one or more subsequent future times following the next future time. Measurement circuitry generates, at the next future time, a new measurement of the aspect of the system. Aggregation circuitry produces an aggregation of the forecast of the aspect of the system for the next future time and of the new measurement of the aspect of the system. The forecast circuitry revises the forecast of the aspect of the system for the one or more subsequent future times using the aggregation.