Theoretical expression of complex systems survivability

Conceptual difference of natural (biological) systems survivability from technical systems reliability is reduced to distinctions of functioning intentions: technical system works for achievement of external aim (for its purpose), whereas the alive system activity is intended for self-preservation. In terms of stochastic modeling the difference of survivability is reduced to feed-back influence of “external” activity of the system to its vitality. (Alive system dies because its activity appears to be futile long enough.) Mathematical expression of these features provides the probabilistic function of life durations. In inference of the general expression (as generating function) the analytics of recurrent events is used.