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:
“An evident principle ... is the principle of justice to all peoples and nationalities, and their right to live on equal terms of liberty and safety with one another, whether they be strong or weak.”
—Woodrow Wilson (1856–1924)
“The man of large and conspicuous public service in civil life must be content without the Presidency. Still more, the availability of a popular man in a doubtful State will secure him the prize in a close contest against the first statesman of the country whose State is safe.”
—Rutherford Birchard Hayes (1822–1893)
“The lifelong process of caregiving, is the ultimate link between caregivers of all ages. You and I are not just in a phase we will outgrow. This is life—birth, death, and everything in between.... The care continuum is the cycle of life turning full circle in each of our lives. And what we learn when we spoon-feed our babies will echo in our ears as we feed our parents. The point is not to be done. The point is to be ready to do again.”
—Paula C. Lowe (20th century)