Keynote 1 — It´s about time

Summary form only given. Cyber-physical systems are integrations of computation, communication networks, and physical dynamics. Although time plays a central role in the physical world, all widely used software abstractions lack temporal semantics. The notion of correct execution of a program written in every widely-used programming language today does not depend on the temporal behavior of the program. But temporal behavior matters in almost all systems. Even in systems with no particular real-time requirements, timing of programs is relevant to the value delivered by programs, and in the case of concurrent programs, also affects the functionality. In cyber-physical systems, temporal behavior affects not just the value delivered by a system but also its correctness. In this talk, I will argue that time can and must become part of the semantics of programs for a large class of applications. To illustrate that this is both practical and useful, we will describe two recent efforts at Berkeley in the design and implementation of timing-centric software systems. On the implementation side, I will describe PRET machines, which redefine the instruction-set architecture (ISA) of a microprocessor to include temporal semantics. Such machines can be used in high-confidence and safety-critical systems, in energy-constrained systems, in mixed-criticality systems, and as a Real-Time Unit (RTU) that cooperates with a general-purpose processor to provide real-time services, in a manner similar to how a GPU provides graphics services. On the design side, I will briefly describe PTIDES, a programming model for distributed real-time systems.