Handbook of Reliability Engineering

Ming J.Zuo, Jinsheng Huang and Way Kuo
In traditional reliability theory, both the system and its components are allowed to take only two possible states: either working or failed. In a multi-state system, both the system and its components are allowed to experience more than two possible states, e.g. completely working, partially working or partially failed, and completely failed. A multi-state system reliability model provides more flexibility for modeling of equipment conditions. The terms binary and multi-state will be used to indicate these two fundamental assumptions in system reliability models.
The following notation will be used:
x i: state of component i, x i=1 if component i is working and zero otherwise;
x: an n-dimensional vector representing the states of all components, x= (x 1, x 2 , , x n );
(x): state of the system, which is also called the structure function of the system;
( j i , x): a vector x whose ith argument is set equal to j, where j=0, 1 and i=1, 2, , n.
A component is irrelevant if its state...