Outline
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Science & Engineering & Art
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Problem & Solution
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Indirection
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Manpower
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Software Design Principles
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And more …
Science & Engineering & Art
Art
Engineering Science
Science & Engineering & Art
Art
Engineering Science
Beauty
Truth
Benefit
Science & Engineering & Art
Art
Engineering Science
Beauty
Truth
For the benefit of people
Problem & Solution
Fundamental Theorem of
Software Engineering
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We can solve any problem by
introducing an extra level of
indirection.
Andrew Koenig
C Traps and Pitfalls
Accelerated C++
“Koenig lookup”
Indirection
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All problems in computer science can be
solved by another level of indirection
Butler Lampson
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… except for the problem of too many
layers of indirection
Kevlin Henney
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Often deliberately mis-quoted with
“abstraction” substituted for “indirection”
What is indirection?
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The ability to reference something using
a name, reference, or container instead of
the value itself
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Manipulating a value through its memory
address
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accessing a variable through the use of
a pointer
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OOP makes use of indirection extensively
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Dynamic dispatch (polymorphism)
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If one woman can produce a
baby in nine months, then nine
women should be able to
produce a baby in one month.
Amdahl’s Law
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Suppose 70% of the operations are
parallelizable
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Brooks' Law
Adding manpower to a
late software project
makes it later
Frederick Brooks
(Intercommunication cost)
Do It Twice
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No software succeeds at the first time
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Software prototyping
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Second-system effect
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Tendency of small, elegant, and successful
systems to have elephantine, feature-laden
monstrosities as their successors
Zawinski’s Law
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Every program attempts to expand until
it can read mail.
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Those programs which cannot so expand
are replaced by ones which can.
Jamie Zawinski
Mozilla
XEmacs
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Software bloat
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Apple iTunes
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Microsoft Windows
Software Design Principles
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Open Close Principle
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Dependency Inversion Principle
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Interface Segregation Principle
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Single Responsibility Principle
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Liskov’s Substitution Principle
Open Close Principle
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Software entities like classes, modules
and functions should be open for
extension but closed for modifications.
Dependency Inversion Principle
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High-level modules should not depend on
low-level modules. Both should depend
on abstractions.
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Abstractions should not depend on
details. Details should depend on
abstractions.
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OOP
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Is-a relation
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Has-a relation
Interface Segregation Principle
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Clients should not be forced to depend
upon interfaces that they don’t use.
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No fat interfaces
Single Responsibility Principle
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A class should have only one reason to
change.
Liskov’s Substitution Principle
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Derived types must be completely
substitutable for their base types.
Barbara Jane Liskov
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Object-oriented design
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Functional implementation
Software artifact
User
interface
Business
rules
Domain
models
Requirements
Design
Code
承上启下
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需求分析和业务建模都是要描述客观事实
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用面向对象的方法去分析与设计
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用最合适的方式去实现
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语言的表达能力存在巨大差异
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要多学几门语言
如何提高（务虚）
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专注
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体会
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感悟
如何提高（务实）
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努力融入到一个有规模的项目中
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一定要做大的东西
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瓶颈往往在最初
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比如编译环境、运行环境的搭建
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学会搜索和独立思考
做些什么？
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真正有价值的是把几年的工作缩减到几个月，
而不是把几天的事情缩短到十五分钟
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有意思的、有技术难度的实际工程中，不要指
望把已经学到的东西恰好应用上去
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学习能力
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应变能力
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清楚原理
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融会贯通
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学会取舍
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与人交流
我做过什么？
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期货
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数据分析
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验证码
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电子表格
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面向特定群体的SNS
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十年献礼工程
我在做什么？
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程序语言（理论与实现）
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数据密集型软件系统的自动生成
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电子商务系统中的服装自动推荐
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“十年献礼工程”
自动化
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科技发展使生产过程自动化程度提高，使劳
动者的智能迅速提高，大大地改变了体力劳
动与脑力劳动的比例，使劳动力结构向着智能
化趋势发展。
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智能机器代替了人的部分脑力劳动，使人们的
劳动方式正在经历着由机械自动化走向智能
自动化，由局部自动化走向大系统管理和控制
自动化的根本性变革。
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科技革命推动了生产规模的扩大，进而推动生
产的分工和协作的广泛发展，并使生产社会化
的程度进一步提高，最终必然会导致生产关系
的变革。
最后⋯⋯
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ACM班是一个很好的平台
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外：树立品牌
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内：资源充足，技术氛围良好
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爱因斯坦：
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关心人的本身，应当始终成为一切技术上奋
斗的主要目标。
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关心怎样组织人的劳动和产品分配这样一
些尚未解决的重大问题，用以保证我们科学
思想的成果会造福于人类，而不致成为祸害。