Operating safety: methods for controlling risks

In industry, the term "operational safety" is increasingly being used. This discipline, which acquired its name and current form mainly over the last half-century in the defence, aeronautics, space, nuclear, telecommunications and transport sectors, is now useful, even indispensable, to all sectors of industry and even other activities.

What does it mean? Dependability is a rich palette of methods and concepts designed to control risks.

Dependability is not a goal in itself, but a means or a set of means: approaches, methods, tools and a vocabulary. The goal that calls for the use of operational safety is best described as "risk control".

• As is usual with this type of word or expression, "operational safety" designates both a set of means and a set of results produced by these means:

  • a particular kind of mindset when it comes to considering systems (particularly industrial systems, but there's no reason to limit ourselves to industry); approaches, methods and tools to understand, characterize and control the effects of hazards, failures, errors, etc;

  • characteristics of systems (products, services, production systems, installations, etc.), expressing the conformity over time (constancy, frequency of conformity) of their behavior and actions with more or less explicit expectations (note the proximity of these notions to quality): safety, reliability, availability, maintainability, even invulnerability, capability, overall cost of ownership, survivability, etc.

By extension, we speak of the "dependability of a system" as the characteristic of that system that enables us to place justified confidence in it. This is deceptively simple. Confidence depends on what we value (safety, productivity, quality...) and the relative values of these characteristics; it is based on a set of approaches and is expressed by a set of characteristics, in particular availability and safety. It is a major advantage of the concept of dependability to bring together approaches motivated by reliability, availability, maintainability and safety, but it is a trap to reduce the result of these approaches to a value (which would be called the system's dependability).

• The characteristics relevant to expressing the foundations of the trust that we place and wish to transmit in our system take forms (names and definitions) specific to the system in question, to the cultures of the players involved and to their vocabularies. Fundamentally, it's always a question of availability and safety, based on basic reliability and maintainability, but the abundance of vocabularies in use...