Abstract: In this paper a systems model is discussed which is sufficiently general to encompass most situations in which component states at time t determine the system state at time t. The model is also useful for complex systems which do not have easily identifiable components.
In terms of this model, notions of ``life length'' are defined and some results for standard models concerning life distributions are generalized.
Key words and phrases: Coherent structures, multi-state coherent systems, new better than used, increasing hazard rate average.