A hierarchical probability model capable of improving the performance and reliability of an availability analysis in a large and complex system is efficiently generated. A hierarchical probability model generation system includes: an independent event analysis unit that specifies independent events about operating conditions of a system on the basis of availability requirements of the system and configuration information of the system, the independent events being calculable independently of each other; an event tree generation unit that generates an event tree using the independent events; and a state transition model generation unit that generates state transition models used to calculate occurrence probabilities of the independent events.
Please help me write a proper abstract based on the patent claims. CLAIM: 1. A hierarchical probability model generation system, comprising: an independent event analysis unit that specifies independent events about operating conditions of a system on the basis of availability requirements of the system and configuration information of the system, the independent events being calculable independently of each other; an event tree generation unit that generates an event tree using the independent events; and a state transition model generation unit that generates state transition models used to calculate occurrence probabilities of the independent events. 2. The hierarchical probability model generation system according to claim 1, wherein the independent event analysis unit includes an operating conditions analysis unit that generates a temporary event tree by analyzing the operating conditions of the system from the availability requirements, a dependence analysis unit that extracts independent sets of configuration elements of the system by analyzing dependence between the configuration elements of the system from the configuration information of the system, and an independent event determination unit that determines independent basic events on the basis of the temporary event tree and the independent sets of the configuration elements of the system, the event tree generation unit generates the event tree using the independent basic events, and the state transition model generation unit generates the state transition models used to calculate occurrence probabilities of the independent basic events. 3. A hierarchical probability model generation system, comprising: an operating conditions analysis unit that generates a temporary event tree by analyzing operating conditions of a system from availability requirements of the system; a temporary state transition model generation unit that generates, on the basis of configuration information of the system, temporary state transition models expressing behaviors of configuration elements of the system; an independent event determination unit that determines independent basic events on the basis of the temporary event tree and the temporary state transition models; an event tree generation unit that generates an event tree using the independent basic events; and an independent basic event state definition unit that specifies a state on a corresponding state transition model for each of the independent basic events and updates the temporary state transition models. 4. A hierarchical probability model generation method, which comprises the steps of: specifying independent events about operating conditions of a system on the basis of availability requirements of the system and configuration information of the system, the independent events being calculable independently of each other; generating an event tree using the independent events; and generating state transition models used to calculate occurrence probabilities of the independent events. 5. A hierarchical probability model generation method, which comprises the steps of: generating a temporary event tree by analyzing operating conditions of a system from availability requirements of the system; generating, on the basis of configuration information of the system, temporary state transition models expressing behaviors of configuration elements of the system; determining independent basic events on the basis of the temporary event tree and the temporary state transition models; generating an event tree using the independent basic events; and specifying a state on a corresponding state transition model for each of the independent basic events and updating the temporary state transition models. 6. A program for causing a computer to function as: an independent event analysis unit that specifies independent events about operating conditions of a system on the basis of availability requirements of the system and configuration information of the system, the independent events being calculable independently of each other; an event tree generation unit that generates an event tree using the independent events; and a state transition model generation unit that generates state transition models used to calculate occurrence probabilities of the independent events. 7. A program for causing a computer to function as: an operating conditions analysis unit that generates a temporary event tree by analyzing operating conditions of a system from availability requirements of the system; a temporary state transition model generation unit that generates, on the basis of configuration information of the system, temporary state transition models expressing behaviors of configuration elements of the system; an independent event determination unit that determines independent basic events on the basis of the temporary event tree and the temporary state transition models; an event tree generation unit that generates an event tree using the independent basic events; and an independent basic event state definition unit that specifies a state on a corresponding state transition model for each of the independent basic events and updates the temporary state transition models.