Robot problems are examined in the context of semantic networks which are used to represent the state of a problem and the operators useful for solving it. Graph transformation algorithms are discussed as an aid to problem solving. Although these form only a small subset of the first-order predicate calculus based systems, considerations such as subgoal circularity, partially specified states and multiple manipulators sharing the same environment may warrant this simplification.

The use of sorting in various computer-related applications such as database management, is well established. Normally, sorting is implemented by employing a combination of hardware and software techniques. In this correspondence the authors examine the utility of serial-shifting nature of the charge coupled device (CCD) and the magnetic bubble memories for achieving low-cost sorting within the secondary storage. The radix-sort method has been found to be very suitable for this purpose. Five different memory organizations implementing radix sort have been described in detail and their relative merits are also outlined.