Predictable real-time software synthesis

Abstract

Formal theories for real-time systems (such as timed process algebra, timed automata and timed petri nets) have gained great success in the modeling of concurrent timing behavior and in the analysis of real-time properties. However, due to the ineliminable timing differences between a model and its realization, synthesizing a software realization from a model in a predictable way is still a challenging research topic. In this article, we tackle this problem by solving a set of sub-problems. The solution is based on the theoretical results for property prediction proposed in Huang et al. (2003, Real-time property preservation in approximations of timed systems. In: Proceedings of 1st ACM and IEEE international conference on formal methods and models for codesign. IEEE Computer Society, Los Alamitos, pp 163–171) and Huang (2005, Predictability in real-time system design. PhD thesis, Eindhoven University of Technology, The Netherlands), where quantitative property relations are established between two absolute/relative “close” real-time systems. This theory basically implies that if two systems are “close”, they enjoy “similar” properties. These results cannot be directly applied in practice though, because a model and its realization typically have infinitely large absolute and relative timing differences. We show that this infinite time gap can be bridged through a sequence of carefully constructed intermediate time domains. Then the property-prediction results can be applied to any pair of adjacent time domains in the sequence. Consequently, real-time properties of the implementation can be predicted from the model. We propose two parameterized hypotheses to characterize the timing differences in the sequence and to guide a correctness-preserving design process. It is shown that these hypotheses can be incorporated in a concrete tool set. We demonstrate the feasibility of the predictable synthesis approach through the design of a railroad crossing system.