Report Number: CS-TR-91-1383
Institution: Stanford University, Department of Computer Science
Title: Temporal proof methodologies for real-time systems
Author: Henzinger, Thomas A.
Author: Manna, Z ohar
Author: Pnueli, Amir
Date: September 1991
Abstract: We extend the specification language of temporal logic, the corresponding verification framework, and the underlying computational model to deal with real-time properties of reactive systems. The abstract notion of timed transition systems generalizes traditional transition systems conservatively: qualitative fairness requirements are replaced (and superseded) by quantitative lower-bound and upper-bound timing constraints on transitions. This framework can model real-time systems that communicate either through shared variables or by message passing and real-time issues such as time-outs, process priorities (interrupts), and process scheduling. We exhibit two styles for the specification of real-time systems. While the first approach uses bounded versions of temporal operators, the second approach allows explicit references to time through a special clock variable. Corresponding to the two styles of specification, we present and compare two fundamentally different proof methodologies for the verification of timing requirements that are expressed in these styles. For the bounded-operatoT style, we provide a set of proof rules for establishing bounded-invariance and bounded-response properties of timed transition systems. This approach generalizes the standard temporal proof rules for verifying invariance and response properties conservatively. For the explicit-clock style, we exploit the observation that every time-bounded property is a safety property and use the standard temporal proof rules for establishing safety properties.