ABSTRACT
Safety can be provided in different ways. Consider a laser on a piece of telecommunications transmission equipment: such a laser is a hazard. In the case of a safety property, there is a finite set of states to be examined to confirm whether that property holds for a particular system. The term real-time is perhaps one of the most confusing and misused terms in software development. A system is real-time simply if its required behavior includes a time constraint. When a software subsystem is invoked, it may fail in one of two ways: It may fail to give a timely answer at all, or it may respond, but with the wrong answer. A programmer may introduce a fault into a program by typing something unintended into an editor. A fault is a passive flaw and is also called a “bug.”
