  The purpose of this report is to look at the measures of importance of
components in systems in terms of reliability. In the first work of Birnbaum
(1968) on this subject, many interesting studies were created and important
indicators were constructed that allowed to organize the components of complex
systems. They are helpful in analyzing the reliability of the designed systems,
establishing the principles of operation and maintenance. The significance
measures presented here are collected and discussed regarding the motivation
behind their creation. They concern an approach in which both elements and
systems are binary, and the possibility of generalization to multistate systems
is only mentioned. Among the discussed is one new proposal using the methods of
game theory, combining the sensitivity to the structure of the system and the
operational effects on the system performance. The presented severity measures
use a knowledge of the system structure as well as reliability and wear and
tear, and whether the components can be repaired and maintained.
