Complete Dynamic Logic of Communicating Hybrid Programs

Abstract: This article presents a relatively complete proof calculus for the dynamic logic of communicating hybrid programs dLCHP. Beyond traditional hybrid systems mixing discrete and continuous dynamics, communicating hybrid programs feature parallel interactions of hybrid systems. This not only compounds the subtleties of hybrid and parallel systems but adds the truly simultaneous synchronized evolution of parallel hybrid dynamics as a new challenge. To enable compositional reasoning about communicating hybrid programs nevertheless, dLCHP combines differential dynamic logic dL and assumption-commitment reasoning. To maintain the logical essence of dynamic logic axiomatizations, dLCHP's proof calculus presents a new modal logic view onto ac-reasoning. This modal view drives a decomposition of classical monolithic proof rules for parallel systems reasoning into new modular axioms, which yields better flexibility and simplifies soundness arguments. Adequacy of the proof calculus is shown by two completeness results: First, dLCHP is complete relative to the logic of communication traces and differential equation properties. This result proves the new modular modal view sufficient for reasoning about parallel hybrid systems, and captures modular strategies for reasoning about concrete parallel hybrid systems. The second result proof-theoretically aligns dLCHP and dL by proving that reasoning about parallel hybrid systems is exactly as hard as reasoning about hybrid systems, continuous systems, or discrete systems. This completeness result reveals the possibility of representational succinctness in parallel hybrid systems proofs.