一、软件 二、软件开发 三、网络环境带来的影响

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

Reuse (Assume have source code, not a commercial product) Ariane 5. Therac-25. British AtC Expectation Significantly lower development costs and time. Amortize costs among all users or uses Assumptions

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

1.类的定义 Rumbaugh对类的定义是： 类是具有相似结构、行为和关系的一组对象的描述

1. 使用UML进行数据库设计 数据库建模传统方法：E-R图。仅对数据建模，不能对行为建模，如触发器、存储过程等建模

1. 包的基本概念 包： 是一个容器。 包的作用： 把一个大的系统分解为多个小的系统。分解是控制 软件复杂性的重要手段：

1.交互图(interaction diagram) 交互图 顺序图

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

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: