Basic Temporal Properties

Abstract

While the Boolean layer consists of Boolean expressions that hold or do not hold at a given cycle, the temporal layer provides a way to describe relationships between Boolean expressions over time. A PSL assertion typically looks in only one direction — forwards from the first cycle (although it is possible to look backwards using built-in functions such as prev(), rose() and fell()). Thus, the simple PSL assertion assert a; states that a should hold at the very first cycle, while the PSL assertion assert always a; states that a should hold at the first cycle and at every cycle following the first cycle — that is, at every cycle.