Sensor information is regularly acquired from a plurality of sensors and stored. For each of the sensors, other sensors whose information is correlated are selected. When sensor information of a sensor is requested from an application program or the like, while if the requested sensor is available the sensor information is acquired directly from the sensor, if the requested sensor is unavailable the sensor information of sensors relevant to the sensor is acquired and the sensor information of the requested sensor is estimated. As a result, in a system comprising a plurality of sensors, sensor information of an unavailable sensor will be estimated in a short period of time.