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

State Machine specifications Define behavior using states and transitions between states

Outline: Software Design Goals History of software design ideas Design principles Design methods Life belt or leg iron?(Budgen)

design: added inheritance, multiple inheritance, and polymorphism to ADT In process added complexity and increased some types of connectivity Lots of claimed advantages -- so far empirical evaluation is not supporting them well

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

Requirements specification: A structured document that sets out the services the system is expected to provide Should be precise so that it can act as a contract between the system procurer and software developer and thus needs to be understandable by procurers and developers

Difficult Person Hostile-aggressie Bullies, cverwhelms, and intimidates cthers nd up to the hostile ade frot atoers-can t accept feedback on t rush into the worst thing that coul happen?)

opyright Nancy Leveson, Sept. 1999 Stage 1: Forming Team members begin to discover what behaviors are acceptable Usually highly unstructured environment Attempt to identify tasks, how to accomplish them Decisions on what information is needed Hesitant participation

Can programming language influence correctness? anguages affect the way we think about problems The tools we use have a profound(and devious) influence on our thinking habits, and, therefore on our thinking abilities?

介绍了计算塑性加工变形力的一种解法工程法的概念及其要 点。举例解析了直角坐标平面应变问题,极坐标平面应变问题,圆柱坐标轴对 称问题以及球坐标轴对称问题。 教学重点:工程法的要点,直角坐标平面应变问题、极坐标平面应变问题、圆 柱坐标轴对称问题以及球坐标轴对称问题的解析