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

Evolutionary Model Prototyping- \Do it twice to assess feasibility to verify requirements May only be a front end or executable specification Or develop system with less functionality or quality attributes °3 approaches:

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

Is there a problem? Why Hard? Syllabus EXamples AAS(FAA Advanced Automation System) FBI CIC IRS Modernization Program

1.1环境监测的目的和分类 1.2监测特点和监测技术概述 1.3环境标准

第一节 代谢概论 第二节 微生物产能代谢

第一节 真细菌（Eubacteria） 第二节 放线菌 第三节 支原体、立克次氏体和衣原体 第四节、蓝细菌（Cyanobacteria） 第五节 古生菌（Archaea）

第一节 原理 第二节 穆斯堡尔谱参数 第三节 实验技术

第一节 X射线的发生与性质 第二节 晶体结构