Pragmatic verification for hybrid and real-time designs

Hybrid and real-time designs are ubiquitous in computing and control systems. There are three prevalent methods for verifying real-time and hybrid systems: simulation, model-checking, and theorem proving. None of these approaches are ideal. This paper presents a verification approach based on refinement. In our refinement framework, we first establish safety properties for a simplified, abstract model of the design and then show that these are inherited by progressively more detailed models. In this approach, we see a hybrid system as a hybrid model: part of the system is modeled with discrete time and state, and other parts are modeled with continuous quantities. The paper illustrates this approach with the design of a simple state-machine for a traffic light.