Runtime Management and Quantitative Evaluation of Changing System Goals

A key challenge in cyber-physical systems is their highly dynamic nature including changing system goals. Therefore, these systems have to autonomously manage their system goals and continuously evaluate their achievement at run-time. However, with the increasing complexity of system goals including, e.g., priorities, dependencies, and conflicts among goals, a binary or qualitative judgement of achievement of goals is not sufficient anymore. Instead, it is necessary to quantify the degree to which the goals are fulfilled in order to balance the cost-benefit ratio at run-time. In this paper, we present a hierarchical and modular goal model that allows for capturing complex relations between subgoals, e.g., dependencies and conflicts. We provide an algorithm that efficiently evaluates gradual achievement of goals at run-time. Due to the modular structure of our model and our evaluation, goals can easily be added, removed, and changed at run-time. With our approach, we a) ease the design of goal-aware autonomous systems by providing an explicit structure that emphasises relations between subgoals, b) provide an automatic quantification of the satisfaction of complex system goals that can be used to, e.g., evaluate autonomous decisions at runtime, and c) enable runtime management of changing system goals.