Distributed task processing within the mobile memory aid system MEMOS

MEMOS is a nomadic computing system to support patients with disturbances in the prospective memory. The system consists of two parts which are loosely connected via GPRS: a mobile electronic device (Personal Memory Assistant - PMA) to remind the patient of important tasks and a Base Station that coordinates the activities of caregivers and notifies them about the result of the task execution. A major requirement of MEMOS is the autonomous operation of the PMA. This is accomplished by avoiding mobile transactions, the specification of temporal aspects in the task description, introduction of different states for tasks of the PMA and the Base Station, and by splitting task and result management. Special XML based languages were developed for data exchange between Base Station and PMA to reflect the temporal aspects of the tasks and for logging the results of task execution.