Too complex for complete analysis Separation into non-interacting subsystems distorts the results The most important properties are emergent Too organized for statistics Too much underlying structure that distorts the statistics Organized Complexity\(Weinberg) Copyright Nancy Leveson, Sept 1999
Abstract Model Specifications Build an abstract model of required software behavior using mathematically defined(perhaps using axioms )types(e. g sets, relations) Define operations by showing effects of that operation on the model Specification includes Model
Formal design Reviews Associated with each of documentation phases Evaluate with respect to Customer requirements Prescribed standards and practices Contractual requirements