The definition of objectives and question of interpretation must be considered when setting up data banks. The objective will determine the type of data to be collected. A hierarchy of data-processing systems exists where the amount of interpretation in the data increases as the order of the system increases. The remarkable continuity of basic data can be embodied in the axiom: “Any fundamental data free of interpretation cannot be discontinuous.” The measurement of space and time remain invariant for all orders of data systems and are essential for relating data containing various amounts of interpretation. In general, only basic data should be exchanged. Where this is not feasible the object described should be clearly defined in space and time.