I. Introduction
Real-time systems interact with the physical environment. They react based on sensing of the physical world and often have to satisfy timing constraints imposed by their interactions. Hard real-time systems are an important class of real-time systems that exhibit safety-critical timing properties, which means that a violation of timing constraints in the system could lead to catastrophic consequences. Thus, hard real-time systems are supposed to be devised and to execute in a unified and rigorous process, for possessing predictability to make them certifiable (i.e., easy to be analyzed). The predictability here refers to the deterministic execution of applications: given a particular set of inputs, applications will always produce the same set of outputs, including both value and timing [1].