Question

Reliability and safety are related but distinct dependability attributes. Describe the most important distinction between these attributes and explain why it is possible for a reliable system to be unsafe and vice versa.

Answer 1

Ensuring system reliability does not necessarily lead to system safety as reliability is concerned with meeting the system specification (the system 'shall') whereas safety is concerned with excluding the possibility of dangerous behavior (the system 'shall not'). If the specification does not explicitly exclude dangerous behavior then a system can be reliable but unsafe.