As information systems were open and complex

the entire problem of survivability analysis was divided into three aspects

i.e.environment

system and analysis process

and models of these aspects were given: system hierarchical model was provided based on the concept of workflow;event scenarios were used to describe the impact of environment on systems

and the environment was presented by grading event and adjusting distribution rate of the event set in different grade;based on FSM

system hierarchical state was provided

which converted the traditional direct survivability analysis based on system state into indirect hierarchical analysis.This analysis model can be applied in quantitative analysis of system survivability because of its event quantification.