The safety life cycle is the series of phases from initiation and specifications of safety requirements, covering design and development of safety features in a safety-critical system, and ending in decommissioning of that system.
The basic concept in building software safety, i.e. safety features in software, is that safety characteristics and behaviour of the software and system must be specified and designed into the system.
The problem for any systems designer lies in reducing the risk to an acceptable level and of course, the risk tolerated will vary between applications.
When a software application is to be used in a safety-related system, then this must be borne in mind at all stages in the software lifecycle.
The process of safety specification and assurance throughout the development and operational phases is sometimes called the ‘safety life cycle’.
The first stages of the life cycle involve assessing the potential system hazards and estimating the risk they pose. One such method is fault tree analysis.
This is followed by a safety requirements specification which is concerned with identifying safety-critical functions (functional requirements specification) and the safety integrity level for each of these functions. The specification may either describe how the software should behave to minimize the risk or might require that the hazard should never arise.
A ‘normal’ process model is then followed with particular attention paid to the validation (inspection, testing etc.) of the system. Part of that validation should be an explicit safety validation activity.
Famous quotes containing the words safety, life and/or cycle:
“A lover is never a completely self-reliant person viewing the world through his own eyes, but a hostage to a certain delusion. He becomes a perjurer, all his thoughts and emotions being directed with reference, not to an accurate and just appraisal of the real world but rather to the safety and exaltation of his loved one, and the madness with which he pursues her, transmogrifying his attention, blinds him like a victim.”
—Alexander Theroux (b. 1940)
“And he thought to himself...., ‘Soul, you have ample goods laid up for many years; relax, eat, drink, be merry.’ But God said to him, ‘You fool! This very night your life is being demanded of you. And the things you have prepared, whose will they be?’”
—Bible: New Testament, Luke 12:17-20.
“Only mediocrities progress. An artist revolves in a cycle of masterpieces, the first of which is no less perfect than the last.”
—Oscar Wilde (1854–1900)