Access system and method for accessing signal data

Signal data from a sensor is stored in a storage device. The signal data is accessed by means access request that includes an identification of a base signal that may indicate the signal data from said sensor and an identification of a derivation to obtain a requested signal from the base signal. An interface extracts the identifications of the base signal the derivation. The interface tests whether stored signal data obtained from the base signal by said derivation is available in the storage device, and if so it returns the stored signal data in response to the access request via the interface. If not signal data is derived from further stored signal data by at least one signal processing operation identified in the derivation.