Chapter 3 - Academic Specification Languages for Reactive Systems

Abstract

This chapter discusses specification languages for reactive systems. Linear time temporal logic (LTL), a specification language, is actually primarily about order and sequencing. LTL assertions describe how basic properties, called propositions, are ordered, that is, what must be before, or after, what. LTL uses Boolean conditions called propositions as basic building blocks. An LTL formula is evaluated given a sequence of truth assignments for Boolean propositions. The LTL extensions that describe real-time constraints and data constraints, also known as time-series constraints are described in the chapter. Other formal specification languages for reactive systems including regular expressions (RE, or regex), interval temporal logic (ITL), graphical interval logic (GIL), computation tree logic (CTL), and TLCharts are also presented in the chapter. An RE represents a requirement as a set of scenarios using set notation. RE are constructed recursively from other RE. Interval temporal logic (ITL) can be loosely characterized as a hybrid of regular expressions and logic. A GIL requirement is a set of legal scenario that is described as an interval defined by its left and right sides. Computation tree logic (CTL) contains, in addition to the always and eventually temporal operators of LTL, two path, or computation, operators: there-exists-a-computation, and all-computations.