上海交通大学：《面向对象分析与设计 Object Oriented Analysis and Design》课程教学资源（PPT课件讲稿）02 Introduction to Visual Modeling

Shanghai Jiao Tong University 上海交通大学 Object Oriented Analysis and Design Introduction to Visual Modeling 上海交通大学软件工程中心

Shanghai Jiao Tong University 上海交通大学软件工程中心 Object Oriented Analysis and Design Introduction to Visual Modeling

Outline ◆Vhat is modeling? Four principles of visual modeling ◆The UML ◆ Process and visual modeling Object Oriented Analysis and Design 2

Object Oriented Analysis and Design 2 Outline  What is modeling?  Four principles of visual modeling  The UML  Process and visual modeling

What Is a Model? A model is a simplification of reality. Object Oriented Analysis and Design 3

Object Oriented Analysis and Design 3 What Is a Model?  A model is a simplification of reality

Why Model? Modeling achieves four aims: Helps you to visualize a system as you want it to be. Permits you to specify the structure or behavior of a system. Gives you a template that guides you in constructing a system. Documents the decisions you have made. You build models of complex systems because you cannot comprehend such a system in its entirety. You build models to better understand the system you are developing. Object Oriented Analysis and Design 4

Object Oriented Analysis and Design 4 Why Model?  Modeling achieves four aims: ▪ Helps you to visualize a system as you want it to be. ▪ Permits you to specify the structure or behavior of a system. ▪ Gives you a template that guides you in constructing a system. ▪ Documents the decisions you have made.  You build models of complex systems because you cannot comprehend such a system in its entirety.  You build models to better understand the system you are developing

The Importance of Modeling Less Important More Important Paper Airplane Fighter Jet Object Oriented Analysis and Design 5

Object Oriented Analysis and Design 5 The Importance of Modeling Paper Airplane Fighter Jet Less Important More Important

Software Teams Often Do Not Model Many software teams build applications approaching the problem like they were building paper airplanes Start coding from project requirements Work longer hours and create more code Lacks any planned architecture ■Doomed to failure ◆ Modeling is a common thread to successful projects Object Oriented Analysis and Design 6

Object Oriented Analysis and Design 6 Software Teams Often Do Not Model  Many software teams build applications approaching the problem like they were building paper airplanes ▪ Start coding from project requirements ▪ Work longer hours and create more code ▪ Lacks any planned architecture ▪ Doomed to failure  Modeling is a common thread to successful projects

Four Principles of Modeling The model you create influences how the problem is attacked. ◆ Every model may be expressed at different levels of precision. The best models are connected to reality. No single model is sufficient. Object Oriented Analysis and Design 7

Object Oriented Analysis and Design 7 Four Principles of Modeling  The model you create influences how the problem is attacked.  Every model may be expressed at different levels of precision.  The best models are connected to reality.  No single model is sufficient

Principle 1:The Choice of Model Is Important The models you create profoundly influence how a problem is attacked and how a solution is shaped. In software,the models you choose greatly affect your world view. Each world view leads to a different kind of system. Process Model Deployment Diagram Design Model Object Oriented Analysis and Design 8

Object Oriented Analysis and Design 8 Principle 1: The Choice of Model Is Important  The models you create profoundly influence how a problem is attacked and how a solution is shaped. ▪ In software, the models you choose greatly affect your world view. ▪ Each world view leads to a different kind of system. Process Model Deployment Diagram Design Model

Principle 2:Levels of Precision May Differ ◆ Every model may be expressed at different levels of precision. The best kinds of models let you choose your degree of detail,depending on: Who is viewing the model. Why they need to view it. 13579e XX BHAL 009 Kr77/ View for Designers View for Customers Object Oriented Analysis and Design 9

Object Oriented Analysis and Design 9 Principle 2: Levels of Precision May Differ  Every model may be expressed at different levels of precision. ▪ The best kinds of models let you choose your degree of detail, depending on: • Who is viewing the model. • Why they need to view it. View for Designers View for Customers

Principle 3:The Best Models Are Connected to Reality All models simplify reality. A good model reflects potentially fatal characteristics 00 00▣00 Object Oriented Analysis and Design 10

Object Oriented Analysis and Design 10 Principle 3: The Best Models Are Connected to Reality  All models simplify reality.  A good model reflects potentially fatal characteristics