Modeling task systems using parameterized partial orders

Abstract

Inspired by work on model-based design of printers, the notion of a parametrized partial order (PPO) has recently been introduced. PPOs are a simple extension of partial orders, expressive enough to compactly represent large task graphs with finite repetitive behavior. We present a translation of a subclass of PPOs to timed automata and prove that the transition system induced by the Uppaal models is isomorphic to the configuration structure of the original PPO. Moreover, we introduce real-time task systems (RTTSs), a general model for real-time embedded systems that we have used to describe the data paths of realistic printer designs. In an RTTS, tasks are represented as PPOs and the pace of a task instance may vary, depending on the resources that are allocated to it. We describe a translation of a subclass of RTTSs to Uppaal, and establish, for an even smaller subclass, bisimulation equivalence between the timed configuration semantics of an RTTS and the transition system induced by the corresponding Uppaal translation. Lastly, we report on a series of experiments which demonstrates that the resulting Uppaal models are more tractable than handcrafted models of the same systems used in earlier case studies.