A Gravitational Task Model for Target Sensitive Real-Time Applications

The commonly used task models for real-time systems focus on execution windows expressing earliest start times and deadlines of tasks for feasibility. Within these windows, execution of tasks is considered of uniform utility.Some applications, however, have target demands in addition: a task should be executed at a target point in time for maximum utility, but can execute around this point, albeit at lower utility. Examples for such applications include control and media processing. In this paper, we present a gravitational based task model to address these issues. Tasks are considered as massive bobs hanging on a pendulum: a single task, left to itself, will execute at the bottom, the target point. If a force, such as the weight of other tasks, is applied, it can be shifted around this point. Thus, tasks´ importance and their utility around target points can be expressed. Additionally, we show a scheduling example of how this model can be used to find the best compromise of tasks´ interests based on the equilibrium state of a pendulum. Nonetheless, this task model is not restricted to a particular scheduling algorithm. Results from a simulation study show the effectiveness of the approach.