1. A method of performing integrated fault-tree analysis on a software controlled system, said software controlled system employing a specific hardware configuration which hardware configuration is selectively operated by means of programmed software comprising the steps performed by a computer of: predicting a critical system output condition manifesting a top-level-event, determining from that predicted condition a set of prior system conditions which caused said event, modifying the system response upon detection of an unblocked patch to said event according to said set of prior system conditions.