Formal Aspects of Computing (1996) 8:294-323 @ 1996 BCS Formal Aspects of Computing Compositional Verification of Real-Time Systems with Explicit Clock Temporal Logic I Ping Zhou, Jozef Hooman and Ruurd Kuiper Department of Mathematics and Computing Science, Eindhoven University of Technology, Eindhoven, The Netherlands Keywords: Real-time; Temporal logic; Semantics; Proof system; Compositionality Abstract. To specify and verify real-time systems, we consider a real-time version of temporal logic called Explicit Clock Temporal Logic. Timing properties are specified by extending the classical framework of temporal logic with a special variable which explicitly refers to a global notion of time. Programs are written in an Occam-like real-time language with synchronous message passing. To show that a program satisfies a specification, we formulate a proof system which is proved to be sound and relatively complete. The proof system is compositional, which makes it possible to decompose the design of a large system into the design of subsystems. This is shown by the verification of a small part of an avionics system. 1. Introduction In this paper we investigate the formal specification and verification of distributed real-time systems. One of our objectives was that the approach should be able to deal with a reasonably realistic language. Therefore, we consider an Occam- like real-time programming language [Occ88] with synchronous message passing along unidirectional channels between concurrent processes. Another aim was to build on existing formalisms and enable easy future extension or adaptation. In Correspondence and offprint requests to: Jozef Hoornan, Department of Mathematics and Computing Science, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven, The Netherlands. e-mail: wsinjh@win.tue.nl 1 This research was supported by ESPRIT-BRA project 3096 "Formal Methods and Tools for the Development of Distributed and Real-Time Systems (SPEC)".