Introduction to the Object-Oriented Approach
OO(Object–Oriented )面向对象
OOOO(Object–Oriented )面向对象OO方法(Object-Oriented Method，面向对象方法，面向对象的方法)是一种把面向对象的思想应用于软件开发过程中，指导开发活动的系统方法，简称OO (Obje ct-Oriented)方法，是建立在“对象”概念基础上的方法学。
对象是由数据和容许的操作组成的封装体，与客观实体有直接对应关系，一个对象类定义了具有相似性质的一组对象。
而每继承性是对具有层次关系的类的属性和操作进行共享的一种方式。
所谓面向对象就是基于对象概念，以对象为中心，以类和继承为构造机制，来认识、理解、刻画客观世界和设计、构建相应的软件系统。
面向对象方法作为一种新型的独具优越性的新方法正引起全世界越来越广泛的关注和高度的重视，它被誉为"研究高技术的好方法"，更是当前计算机界关心的重点。
十多年来，在对OO方法如火如荼的研究热潮中，许多专家和学者预言：正象70年代结构化方法对计算机技术应用所产生的巨大影响和促进那样，90年代OO方法会强烈地影响、推动和促进一系列高技术的发展和多学科的综合。
一、面向对象方法的由来与发展回顾历史可激励现在，以规划将来。
OO方法起源于面向对象的编程语言（简称为OOPL）。
50年代后期，在用FO RTRAN语言编写大型程序时，常出现变量名在程序不同部分发生冲突的问题。
鉴于此，ALGOL语言的设计者在ALGOL60中采用了以"Begin……End"为标识的程序块，使块内变量名是局部的，以避免它们与程序中块外的同名变量相冲突。
这是编程语言中首次提供封装（保护）的尝试。
此后程序块结构广泛用于高级语言如Pascal 、Ad a、C之中。
60年代中后期，Simula语言在ALGOL基础上研制开发，它将ALGOL的块结构概念向前发展一步，提出了对象的概念，并使用了类，也支持类继承。
70年代，Sm alltalk语言诞生，它取Simula的类为核心概念，它的很多内容借鉴于Lisp语言。
计算机专业英语考试试题及答案
计算机专业英语考试试题及答案一、选择题1. Which of the following is NOT a programming language?A. JavaB. PythonC. HTMLD. CSS2. What does the acronym "SQL" stand for?A. Structured Query LanguageB. Simple Query LanguageC. Script Query LanguageD. Secure Query Language3. Which protocol is commonly used for sending and receiving emails?A. FTPB. HTTPC. SMTPD. TCP4. What does the term "CPU" refer to?A. Central Processing UnitB. Computer Processing UnitC. Central Program UnitD. Computer Program Unit5. Which of the following is NOT a type of network topology?A. StarB. RingC. MeshD. Scroll二、填空题1. HTML stands for Hypertext Markup Language, which is used for ____________.2. The process of converting source code into machine code is called ____________.3. IP address stands for ____________.4. The act of copying files from a remote server to a local computer is known as ____________.5. The programming language developed by Apple Inc. for iOS and macOS is ____________.三、简答题1. What is the difference between a compiler and an interpreter? Provide examples of programming languages that use each of these methods.2. Explain the concept of object-oriented programming (OOP) and provide an example of a programming language that utilizes this paradigm.3. Describe the client-server model and provide an example of a commonly used protocol within this model.四、论述题Discuss the impact of artificial intelligence (AI) on various industries. Provide examples of how AI is being used in fields such as healthcare, finance, and transportation. Analyze the potential benefits and challenges of implementing AI in these industries.答案：一、选择题1. C. HTML2. A. Structured Query Language3. C. SMTP4. A. Central Processing Unit5. D. Scroll二、填空题1. creating and structuring the content of a webpage2. compilation3. Internet Protocol4. downloading5. Swift三、简答题1. A compiler translates the entire source code into machine code before the program is executed. Examples of languages that use compilers are C, C++, and Java. On the other hand, an interpreter translates and executes the source code line by line. Python and Ruby are examples of languages that use interpreters.2. Object-oriented programming (OOP) is a programming paradigm that organizes data and functions into reusable objects. It focuses on the concept of classes and objects, allowing for code reuse and encapsulation. An example of a programming language that uses OOP is Java, where objects are instances of classes and can interact with each other through methods and attributes.3. The client-server model is a distributed computing architecture wherea server provides services or resources to multiple clients. The clients request and receive these resources through the network. An example of a commonly used protocol within this model is the Hypertext Transfer Protocol (HTTP), which is used for communication between web browsers (clients) and web servers.四、论述题Artificial intelligence (AI) has had a significant impact on various industries. In healthcare, AI is being used for diagnoses and treatments, analyzing medical images, and personalized medicine. For example, AI-powered algorithms can help detect diseases like cancer at an early stage, leading to better treatment outcomes. In finance, AI is utilized for fraud detection, algorithmic trading, and customer service. AI algorithms can analyze large amounts of financial data to identify patterns and make accurate predictions. In transportation, AI is being employed for autonomous vehicles, traffic management, and logistics optimization. Self-driving cars, for instance, use AI algorithms to navigate and make decisions on the road.The implementation of AI in these industries brings about many benefits, such as increased efficiency, improved accuracy, and cost savings. AI systems can process and analyze vast amounts of data much faster than humans, leading to faster and more accurate results. However, there are also challenges to consider. Privacy and security concerns arise as AI systems handle sensitive information. There is also the worry of job displacement, as AI automation may replace certain human tasks. Additionally, ethical considerations need to be addressed, such as bias in algorithms and the potential for AI to be used for malicious purposes.Overall, the impact of AI on various industries is undeniable. It has the potential to revolutionize healthcare, finance, transportation, and many other sectors. However, careful implementation and regulation are necessary to ensure its responsible and beneficial use.。
计算机专业毕业设计论文外文文献中英文翻译——java对象
1 . Introduction To Objects1.1The progress of abstractionAll programming languages provide abstractions. It can be argued that the complexity of the problems you’re able to solve is directly related to the kind and quality of abstraction。
By “kind” I mean，“What is it that you are abstracting?” Assembly language is a small abstraction of the underlying machine. Many so—called “imperative” languages that followed （such as FORTRAN，BASIC, and C) were abstractions of assembly language。
These languages are big improvements over assembly language，but their primary abstraction still requires you to think in terms of the structure of the computer rather than the structure of the problem you are trying to solve。
The programmer must establish the association between the machine model (in the “solution space，” which is the place where you’re modeling that problem, such as a computer) and the model of the problem that is actually being solved (in the “problem space,” which is the place where the problem exists). The effort required to perform this mapping, and the fact that it is extrinsic to the programming language，produces programs that are difficult to write and expensive to maintain，and as a side effect created the entire “programming methods” industry.The alter native to modeling the machine is to model the problem you’re trying to solve。
C# 英文教材01
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Object-Oriented Methodology － Example
我们首先需要有车
要有人设计车
类(class)
要有工程图纸 造出真正的汽车
对象(object) 对象(object)
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Identify the possible states of the following objects： 1. A cell phone 2. A stereo Answer： 1. States of a cell phone：Off，Ring， Vibrate，and Call 2. States of a stereo：Play，Pause， Rewind and Forward
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Object-Oriented Methodology
Object-orientation（面向对象） is a software development methodology that is based on modeling a real-world system. An object is the core concept involved in object orientation. You can think of an object oriented model as a collection of objects and their interrelationship.
计算机专业必读技术书籍
【38】 “面向模式的软件体系结构 卷1：模式系统”（ Pattern-Oriented Software Architecture， Volume 1： A System of Patterns）
漫长的三年过去了，我们摸爬滚打，没有指路的明灯。我也在摸索中走了不少的弯路，向我的软件班的同学引荐别人推荐几本好书（我也是在查漏补缺），希望有志者能少走些弯路。
一、 ቤተ መጻሕፍቲ ባይዱ学哲学和管理哲学
【1】 “程序开发心理学”（The Psychology of Computer Programming ： Silver Anniversary Edition）
八、 软件维护和重构
【53】 “重构－改善既有代码的设计”（Refactoring： Improving the Design of Existing Code）
九、 配置管理和版本控制
【54】 “版本控制之道 —— 使用CVS”（程序员修炼三部曲第一部：Pragmatic Version Control Using CVS）
【21】 “人件集 —— 人性化的软件开发”( The Peopleware Papers： Notes on the Human Side of Software)
【22】 “人月神话”（The Mythical Man-Month）
【23】 “软件工程 — 实践者的研究方法（原书第5版）”（Software Engineering： A Practitioner's Approach， Fifth Edition）
面向对象编程(oop)名词解释
面向对象编程（Object-Oriented Programming, OOP）是一种程序设计范式，它将现实世界中的事物抽象为程序中的对象，并通过对象之间的交互来实现各种功能。
在面向对象编程中，对象可以是具体的实体，也可以是抽象的概念，它们都可以拥有属性和方法，通过这些属性和方法可以描述和操作对象的特性和行为。
面向对象编程是现代软件开发中最常用的编程范式之一，它具有高内聚、低耦合的特点，能够提高代码的复用性、可维护性和可扩展性。
面向对象编程的核心思想包括封装、继承和多态。
1. 封装（Encapsulation）封装是面向对象编程的重要特性之一，它通过将数据和方法封装在对象内部，隐藏对象内部的实现细节，只暴露特定的接口给外部使用，从而保护数据的安全性和完整性。
封装可以使对象的内部状态只能通过指定的方法进行访问和修改，提高了程序的安全性和稳定性。
2. 继承（Inheritance）继承是面向对象编程中的另一个重要概念，它允许一个类（子类）继承另一个类（父类）的属性和方法，并且可以对其进行扩展或修改。
通过继承，可以减少重复的代码，提高代码的复用性和可维护性，同时也能够构建出更加抽象和通用的数据模型。
3. 多态（Polymorphism）多态是面向对象编程的另一个重要特性，它允许不同的对象对同一个消息做出不同的响应，即同一操作作用于不同的对象上可以有不同的结果。
通过多态，可以实现更加灵活的程序设计，减少代码的复杂度，提高程序的可扩展性和可维护性。
面向对象编程是软件开发中非常重要的一部分，它已经广泛应用于各种编程语言和评台上。
通过面向对象编程，可以更加方便地描述和模拟现实世界中的问题，提高程序的抽象能力和可扩展性，减少程序设计和开发的复杂度，从而提高软件开发的效率和质量。
面向对象编程是一种强大而灵活的编程范式，它通过封装、继承和多态等特性，使代码更加具有可读性、可维护性和可重用性，是现代软件开发不可或缺的一部分。
Object-Oriented Analysis and Design
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To talk about agile practices and OOA&D
CS 292 Object Oriented Design 2
Now it’s time to start reading Head First Object-Oriented Analysis and Design Read Chapters 1 - 3, and 8 for next week.
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CS 292
Object Oriented Design
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Generalization and inheritance
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Objects are members of classes which define attribute types and operations Classes may be arranged in a class hierarchy where one class (a super class or base class) is a generalization of one or more other classes (subclasses)
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Object Oriented Design
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Advantages of inheritance
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It is an abstraction mechanism which may be used to classify entities It is a reuse mechanism at both the design and the programming level The inheritance graph is a source of organizational knowledge about domains and systems
Chapter 1 Introduction to Object-oriented programming and software Development
Introduction to Object-Oriented Programming with Java--Wu
Chapter 1 - 5
Instance-of Relationship
Before you can create instances of a class, the class must be defined.
A class data value is used to maintain information
shared by all instances or aggregate information about the instances. For example, minimum balance is the information shared by all Account objects, whereas the average balance of all Account objects is an aggregate information.
Chapter 1 - 10
Summary of Class and Object Icons
<result>
<Class Name>
Squared corners are used for a class and class methods.
An instance method icon is drawn in a dotted line.
to be able to handle the received message.
A method defined for a class is called a class method,
and a method defined for an object is called an
抽象类作文英语模版
抽象类作文英语模版英文回答：Introduction.In the realm of object-oriented programming, the concept of abstraction occupies a pivotal position. Abstraction allows us to encapsulate the essential characteristics and behaviors of real-world entities into classes, providing a structured and reusable blueprint for creating objects. Among the various class types, abstract classes hold a unique distinction, serving as a foundation for defining common interfaces and preventing the instantiation of incomplete or invalid objects.Definition of an Abstract Class.An abstract class is a class that cannot be instantiated directly but must be subclassed to create concrete objects. It serves as a template that defines theinterface and shared functionality of a group of related classes. By declaring at least one of its methods as abstract, an abstract class ensures that subclasses must implement the method with specific behavior before they can be used.Characteristics of Abstract Classes.1. Cannot be instantiated: Abstract classes cannot be used to create objects directly. They exist solely to provide a blueprint for subclasses to inherit and expand upon.2. Contain abstract methods: Abstract classes declare one or more abstract methods, which are method signatures without implementations. Subclasses must override these abstract methods with concrete implementations to provide specific functionality.3. May contain concrete methods: In addition to abstract methods, abstract classes can also include concrete methods, which provide default implementationsthat subclasses can inherit or override.4. Act as a contract: Abstract classes define a contract that subclasses must adhere to. By implementing the abstract methods, subclasses guarantee that they possess the required functionality and follow the established interface.Uses of Abstract Classes.Abstract classes offer various advantages, including:1. Enforce method signatures: They ensure that subclasses implement the required methods with the correct signatures, preventing inconsistencies and enforcing a common interface.2. Promote code reusability: By providing a shared interface, abstract classes facilitate code reusability across subclasses, reducing duplication and promoting maintainability.3. Prevent incomplete objects: By prohibiting direct instantiation, abstract classes prevent the creation of invalid or incomplete objects, ensuring that only objects with complete and consistent functionality are created.4. Promote polymorphism: Abstract classes support polymorphism, allowing objects of different subclasses to be treated as objects of the abstract class, fostering flexibility and extensibility in code.Example of an Abstract Class.Consider the following abstract class representing the concept of a shape:java.public abstract class Shape {。
C++钱能
《C ++程序设计笔记(钱能主编)》第一部分基础编程（The Basic Programming）概述（Introduction）1、过程化程序设计（Procedural Programming）：程序（Programs）：=算法（Algorithms）+数据结构（Structures）（大型软件主要是Struct 之间的组合）描述问题只需3种基本控制语句：顺序、选择、循环。
每个模块，其内聚性（aggregation）越强，外联型（association）越小，则模块独立性越好。
2、对象化程序设计（Objectified Programming）：程序（Programs）：=算法（Algorithms）+抽象数据类型(ADS：Abstract Data Structure)。
这里的程序便可形成一种称之为类（Class）的对问题的描述；程序（Programs）：=（对象（Object），对象（Object），…）。
这样就适应问题跨度更大，抽象层析更高，编程模块更加灵活高效。
第1章基本编程语句（Basic Programming Statements）1、C++的基本编程语句包括：说明语句、复制语句、表达式语句和过程控制语句，其中过程控制语句又包括：顺序语句、选择语句和循环语句。
注：这里，不考虑跳转语句（goto），goto的使用，不太适合过程化的思想。
2、在C/C++中，要将计算的结果保存在存储空间就必须指出存储空间的位置：在C/C++中，存储数据的名称有两种：①成为变量（或常量），是C\ C++内部数据类型定义而产生的。
②对象（或常对象），由程序员定义的类（Class）而产生的。
说明语句又分为：声明（Declarative）和定义（Definition）如果要在之前的程序中使用该程序之后定义的变量、对象或函数，则应该在程序之前对之后的部分进行声明，或者在其他文件中使用，亦如此。
变量的初始化与赋值。
course1
class
Definition:
describes a set of objects that have identical characteristics (data elements) and behaviors (functionality). Examples:
Light
bulb.
Polymorphism
An example: animation
demonstration analysis of the problem. hierarchy of the classes source code of the example
Fundamental concepts:
Course outline (continued)
C9: a more powerful preprocessor C10: to avoid name clash C11: References & the Copy-Constructor C12: functions with funny names C13: new and delete C14: code reuse by composition and inheritance C15: Polymorphism & Virtual Functions C16: Templates
Base class: contains common characteristics and behaviors shared by all of the derived classes Derived classes: additional functionality (flip), different functionality (area)
第五版前言翻译
Perface （前言）Background （背景）The history of database research over the past 30 years is one of exceptional productivity that has led to the database system becoming arguably the most important development in the field of software engineering.1.Exceptional /ik’sepʃənəl/ adj. 非常好的，杰出；2.Arguable /’a:gjuəbəl/ adj. Not certainly true or correct and therefore easy or doubt. 有疑问的；译：过去30多年的数据库研究历史是杰出成就之一，同样也导致了数据库可能变成软件工程领域最重要的发展。
The database is now the underlying framework of the information system and has fundamentally changed the way many organizations operate. 译：现在，数据库是信息系统的底层框架，也从根本上更改了许多公司的操作。
In particular, the developments in this technology over the last few years have produced systems that are more powerful and more intuitive to use 3.intuitive /in’tju:iətiv/ adj. An intuitive idea is based on feelings rather than on knowledge or facts （想法）凭直觉获知。
卡雷尔 第1章
卡雷尔+ +第1章Karel J. Robot 卡雷尔j的机器人A Gentle Introduction to the Art of Object-Oriented Programming in Java一个温柔的介绍面向对象的程序设计艺术在JavaJoseph Bergin约瑟夫贝尔然Mark Stehlik马克斯特赫利克Jim Roberts吉姆罗伯茨Richard Pattis理查德PattisThis manuscript has not been published.这手稿尚未发表。
It is Copyright, Joseph Bergin.它的版权，约瑟夫贝尔然。
1 The Robot World 1，机器人世界This chapter introduces a class of robots and sketches the world they inhabit.本章介绍了机器人类和素描他们所居住的世界。
In later chapters, where a greater depth of understanding is necessary, we will amplify this preliminary discussion.在以后的章节中，凡有更深入的了解是必要的，我们将扩大这个初步的讨论。
1.1 The Robot World 1.1机器人世界Robots live in a world that is unexciting by today's standards (there are no volcanoes, Chinese restaurants, or symphony orchestras), but it does include enough variety to allow robots to perform simply stated, yet interesting tasks.机器人生活的这个世界是标准扫兴今天的（有没有火山，中餐馆，或交响乐团），但它包括足够的品种，让机器人执行简单地说，但有趣的任务。
Università di Pisa
A Framework for Comparing Type Systems forDatabase Programming LanguagesAntonio Albano1, Alan Dearle2, Giorgio Ghelli3, Chris Marlin4, Ron Morrison2, Renzo Orsini3 & David Stemple51Dipartimento di Matematica e InformaticaUniversità di UdineVia Zanon 6 - 33100 UdineItaly.3Dipartimento di InformaticaUniversità di PisaCorso Italia40 - I-56100 PisaItaly.5Department of Computer ScienceUniversity of MassachusettsAmherst MassachusettsU.S.A.2Department of Computational ScienceThe University of St AndrewsSt AndrewsScotland.4Department of Computer ScienceThe University of AdelaideAdelaideSouth AustraliaAustralia. AbstractSeveral proposals have been published in recent years for database programming languages(DBPLs), many of which have been object-oriented. Our goal in this paper is not to argue for oragainst specific solutions, but simply to provide a framework for comparing certain critical pointsof type system design. This framework may be used in the description of a DBPL. It is our hopethat the framework will promote clear communication among designers and developers of DBPLs.1IntroductionAt the Second Object-Oriented Database Workshop [OO88], the first author posed a set of questions as a way of urging people to be clear when talking about types and/or classes. This brief paper expands on those questions in an effort to provide a framework for describing type systems that can be used to compare programming languages in a meaningful manner. We have divided the questions to be asked into five areas. The first is discussed in Section 2 and has to do with the nature of the type system.Section 3 deals with the expressiveness of the type definition capabilities and lists some of the type constructors that could appear in a type system. This section also addresses the limitations on expressibility in the type definition language and the constraints that can be expressed in the language, both explicitly and implicitly. It is also this section which covers polymorphism in the type system.Section 4 is devoted to details of the value space. The issues addressed in this section include questions such as whether each type has equality defined on its values, whether functions can be values in a type, and whether there are to be objects as well as values in types.Section 5 deals with relationships between types, covering the question of type equivalence and how concepts such as abstract types and object types relate to each other. In Section 6, issues concerned with subtypes of types are explored, such as whether subtypes arise implicitly or explicitly, and the nature of subtyping rules in the type system.The notion of a class as a type concept is addressed in Section 7, and the database aspects of the type system, such as persistence, are dealt with in Section 8. After some miscellaneous issues in Section 9, a few brief conclusions are presented in Section 10.We have made an attempt to avoid being normative in presenting these questions. Similarly, we have mostly avoided definitions which may over constrain the utility of the framework. Our aim is to give a framework that facilitates good communication among the designers and developers of database programming languages, rather than to prescribe or proscribe certain sets of features of type systems. Our hope is that we will make it easier to compare different languages with respect to the semantics of their types; this is something which has been difficult to do in the past.2The Nature of the Type System2.1Does the language have a type system?The type system of a language is the manner in which the set of values over which a computation may range is partitioned into subsets, the types, such that only values within a particular type may occur at a particular point in the computation specified in the language. A language without such a property (or, which is equivalent, with just one type) is called type-free. An example of a type-free language is the λ-calculus.2.2Is the language strongly typed? Is type checking static or dynamic?A language is strongly typed if all computations are checked for type errors. A strongly typed language is statically checked if all type errors are discovered at compile time, and dynamically checked if type errors are only discovered at run time. There may be other times, such as link time, when checking may be performed. A mixture of checking times is also possible.2.3How is type checking used in data definition and for operations?Type checking is intended to signify a check made on a program to determine if types are defined and/or used in a consistent manner. The type checker is the program which performs this task. There are two principal forms of checks, one which concerns only the definition of database schemata, and another which concerns the use of data:•Checks for database schema well-formedness: In this case the data definitions are checked for consistency. This is usually the case of a data definition language (DDL) of a databaselanguage which deals with data definition.•Checks for correct utilisation of values: In this case, all computations in the program are checked to detect whether a value appears in an improper place in a computation. In general,for each type T, there is a set of operations O T that can be applied to its values; a value of type Tis misused with respect to its type (i.e., a type error occurs), if an operation which does notbelong to O T is applied to it.2.4Is the type system used only for error checking or also for thespecification of implementation details?Type systems evolved in programming languages as a means of specifying implementation details, such as the layout of storage. In certain languages, such as typed functional languages, this role has diminished. In other languages, a major motivation is that of data modelling.2.5If the previous questions do not fully cover the nature of the type system,what is missing from the description of the system?3ExpressivenessThe expressiveness of a type system concerns the following aspects:•The set of primitive types offered (integers, strings, booleans, etc.) and type constructors (records, arrays, functions, unnamed types, abstract data types, etc.) with the associated operations, such asconstructors, selectors and iterators.•The kind of polymorphism of the system, e.g. the mechanism used to express the fact that a function can be legally applied to all values belonging to a family of related types.These points are explored in the following sections.3.1What primitive types and type constructors are available in the language?Are there restrictions on the combinations of type constructors or the form of recursion?Here, we use the terminology of Cardelli and Wegner [CW85] if they discussed the constructor. Among the type constructors which can be found in programming languages, we have:•Primitive types: string, integer, boolean, floating point, bit string, trivial type (one element type), enumerated type.•Cross product (pair, tuple).•Record (labelled cross-product).•Discriminated union.•Variant (labelled disjoint sum).•Array.•List.•Set.•Sequence.•Function.•Reference.•Mutable value.•Predicate subtype (as in a subrange of integers – it takes a type and a predicate on elements of the type and produces a type having only those elements of the input type that satisfy the predicate).•Parameterisation (abstraction over an expression defining a type to define new type constructors, such as tree of something or stack of something).•Abstract data type (selective hiding over a type definition).•Recursive type definition, such as:rec type Department := [Name: string andEmployees: seq Employee]and Employee := [ Name: string and Dept: Department ]3.2What kinds of polymorphism are supported by the type system?Polymorphism means that a single function can act on values of a well defined set of related types. There are two popular kinds of polymorphism:•Universal polymorphism, which has two forms:-Inclusion polymorphism means that a subtype relation is defined on types such that if B is a subtype of A, any function that can be applied to A can also be applied to B.-Parametric polymorphism means that a function can have an implicit or explicit type parameter which determines the type of value parameters and the type of the result. It is called implicitpolymorphism when the type parameter is deduced from the type of value parameters, and explicitpolymorphism when the type parameter must be specified explicitly.•Ad hoc polymorphism or overloading, which occurs where a function acts differently for each allowable type. The arithmetic operator “/” (divide), which acts on integers and reals, is anexample of an ad hoc polymorphic operator.4Types and valuesThis section deals with some properties of the relationship between values and types.4.1What are the properties that are possessed by values of all types? Is therea concept of first class values? What are the properties that define firstclass values? Do all types have these properties?Obviously, not all values of all types can be treated the same. However, there are normally operations and properties that are shared by many if not all types. These often include the ability to be bound to identifiers, stored in memory locations, passed as parameters to functions and returned as results. These properties can be used to define the concept of first class values.4.2Are there values that can be typed that have special properties not sharedby all values? What are they and how are they special? Among these might be functions, mutable values and types themselves.In some languages functions are first class values of a specific family of types: the function types. In other languages, there is a way to define, store, identify and use ordinary (first class) values and another way to define and use functions.The same situation might exist for mutable values. If the mutability of a value can be controlled in a type system, is this control explicit or implicit? If implicit, what structures include it implicitly? If explicit, with what constructors can it be included?4.3Does the type system allow the construction of objects?We regard an object as an entity with a local state and equipped with a set of operations. An object has an “identity”which is independent of its state.4.4Is every value an object, or do both objects and non-object values exist?Are objects first class values? What is the exact distinction (if any)between objects and first class values in the language? How do types ofobjects fit into the type system?4.5What is the semantics of the equality relation?Among the different possible semantics for equality we have:•Typed structural equality: two values are equal if the same sequence of legally typed selectors applied to either of them will give the same result.•Equality based on sameness: some values can have an “identity” which is independent of their value; these values are often called objects. Sameness tests if two expressions evaluate to the“same” object.•Low-level structural equality: two values are equal if their internal representation by the run-time support is equal.•User defined equality: some languages allow the user to define equality.•Others.•Mixed equality: different combination of the preceding ones are possible, and present in some programming languages.4.6Is there a concept of null value? Are there different kinds of null values?How do they interact with the equality relation?5Relationships among TypesIn this section, we aim to elicit the properties of type interrelationships, such as those involved in type equivalence, subtyping and inheritance.5.1What is the nature of type equivalence?A type equivalence rule is used by the type checker in determining whether a value has the correct type for its context. Type equivalence rules are important and complicated where program and data are separately prepared. There are two common forms of type equivalence:•In name equivalence, two values have equivalent types if the types share the same declaration.•In structural equivalence, two values have equivalent types if the types have isomorphic structures.5.2Does the language offer abstract, “concrete”, and “unnamed” types?Abstract types permit new types to be defined by specifying a representation type and the new type's operators, i.e.a set of operations which take as parameters and/or give as results values belonging to this new type. The representation type is hidden in an abstract type. A “concrete” type definition is an association between a name and a type expression which makes that name completely equivalent to that expression; so a concrete type is not a new type but is a new denotation for the representation type. A language offers “unnamed” types when a type expression can be used in situations where a type identifier could appear, for example to denote the type of the parameters of a function, the type of the fields of a record, and so on. As a consequence, an abstract type is different from any other type, as well as from its representation type, while a concrete or unnamed type is equal to its defining type expression.Another possibility for defining new types is the semi-abstract type: the new type is different from any other type and from the representation type but it inherits the predefined operators on the representation type. Consider for instance, a semi-abstract type Person represented as a record type. In this case, the selection operators on the representation record type can be used to extract information from values of type Person.5.3How are abstract types related to object types?Object types may be a special case of abstract data types. Alternatively, they may be the only kind of abstract data type that can be built in the language or defined through an unrelated mechanism.5.4Does the language offer a module mechanism and, if so, what are itsfeatures? Are modules related to abstract data types? Are modules realised through a type constructor or are they a concept unrelated to the typesystem?Abstract types and modules are related as they both serve a software engineering function of detail hiding. They both provide "encapsulation", the insulation of an “interface”, i.e. the means of interacting with a module or abstract type, from a “body”, which is the implementation of the module or of the abstract type definition. In addition to data encapsulation, modules are used as unit of recompilation when the implementation of the operations in the body is modified.6Types and subtypes6.1Is the subtype relation defined implicitly or explicitly?In general, there are two ways in which a language can define a subtype relation among two types A and B:•implicitly: types A and B are defined independently, but the subtyping rules specify that one isa subtype of the other, or•explicitly: type B is specified to be a subtype of A.This issue is related to the type equivalence relation, as the first choice is similar to structural equivalence and the second to name equivalence. Both the possibilities can be present at once in a language.6.2What subtyping rules are adopted in the type system? Is there any notionof closure in subtyping? If so, are subtypes restricted to closed subtypes, or can closure be specified and enforced or verified?By closure, we mean the following: if B is a closed subtype of A, then any operation that accepts values of type A and produces values of type A will produce a value of type B if applied to B type values.6.3Can redefinitions be made going down the subtype hierarchy? If so, whatmay be redefined and under what control?For example, in object-oriented languages it is common to allow the redefinition of methods when declaring a subtype. This may include redefinition of the type and semantics of the method.6.4Is the subtype graph single or multiple?How are name conflicts resolved?A new type can be defined as an immediate subtype of only one type (single hierarchy), or as a subtype of several types (multiple hierarchy). In both cases, any subtype can have multiple supertypes, in the first case because the subtype relation is transitive. Of course, when subtypes are inferred and not explicitly defined (see 6.1), a multiple hierarchy results.A name conflict occurs when the same attribute is defined differently in more than one supertype. A common approach is to solve the conflict on the basis of the order of supertype specification.7Classes and subclasses7.1Does the language have a concept of class?If so, what is it?One possible definition is for a class to be characterised by the type of its elements, and by the set of the elements of that type currently in existence.7.2How are a class and the type of its elements related?When a database language has a type system in the sense previously defined, it is important to distinguish between the definition of the classes, i.e. sets of values which populate the database, and the definition of types. In fact types are sets of all possible values, while classes are sets of actual values, i.e., values currently present in the database. In many languages a class and the type of its elements are defined through a single construct and sometimes are given only one identifier, while in others the two concepts are clearly distinguished. Another related issue is whether all the values built in a program which belong to the type associated to a class automatically belong to the class or whether an explicit insertion operation is needed.7.3Does the language have a distinction between subtypes and subclasses?This question makes sense in languages with classes and types as previously discussed. When there is a separation between these two concepts, there could be a concept of subclass in addition to that of subtype. A subclass concerns the extensional aspect of the isa relation: if we are interested both in Persons and Females, we have two different and essential facts: the type Female is a subtype of the type Person, because all the possible Females are a subset of all the possible Persons, and the class Females is a subclass of a class Persons because Females is a subset of all the actual Persons at all times.In systems where the subclass relation is distinct from the subtype relation, the next four questions mimicking 6.1 to 6.4 need to be answered.7.4Is the subclass relation defined implicitly or explicitly?7.5What subclass rules are adopted in the type system?7.6Can redefinitions be made going down the subclass hierarchy? If so, whatmay be redefined and under what control?7.7Is the subtype graph single or multiple? How are name conflicts resolved?7.8Does the language have single or multiple superclasses? Is it the case thatthe set of all superclasses of a class must have a maximum element?7.9How are subclasses populated?There are several possibilities:• A subclass can be populated by creating elements with an appropriate constructor. These elements also appear as elements of its superclasses, because of the semantics of the subclass relation.• A subclass can be populated by moving objects from a superclass into the subclass. So objects can change the most specific type to which they belong during their life. For instance, a personcan become a student, then an employee, and finally just a person again.• A subclass can be populated automatically if it can be defined as containing all the elements of the superclass which satisfy a certain condition.7.10Can objects be removed from classes and subclasses? Can objects bedeleted?When an object is removed from a class, because of the semantics of the subclass relation, it is removed also from its subclasses; but when it is removed from a subclass it might be left in the superclasses. Does an operator exist for the explicit deletion of an object, or is this task left to the garbage collector? If an object can be explicitly deleted, how are references to it managed? Has the deletion of an object an effect on its components?7.11Are subclasses of the same superclass disjoint? Is the union of the sets ofthe elements of the subclasses equal to the set of the elements of thesuperclass?8Database Issues8.1Is persistence orthogonal to the type system?Persistence is sometimes a characteristic of a specific type constructor, in which case it is a type issue. Orthogonality of persistence and the type system means that any value can be made persistent, in which case it is not a type issue.8.2What kinds of database schema evolution are supported?Schema evolution means the possibility of making changes to the database schema after the database has been populated. To fully understand this important feature of database programming languages it is useful to distinguish changes which have no effects on application programs and existing data, changes which require only the recompilation of application programs, and changes which require modifications to existing programs and data.9Other issues9.1To what extent is type inference employed in the language?9.2Is there any theory supporting the type system?Does, for example, the set of type definitions build a theory of the application?9.3Are there implementation factors that are essential to the understanding ofthe system?For example, do the binding mechanisms provide the necessary semantics for fully understanding the system?9.4Are there issues that are not covered in the previous questions that areimportant to understanding the type system?9.5What is the status of the implementation of the system?10ConclusionsA framework for the comparison of the type systems in database programming languages has been presented. We have avoided being normative, to allow for the greatest flexibility in the languages being compared. Similarly, we have mostly avoided definitions which may over constrain the utility of the framework. We hope that our framework is comprehensive, but realise that this is unlikely given that the study of these issues has only recently begun. Consequently, we have attempted to create an open-ended framework and we invite others to use the framework to describe their languages, extending and refining it where necessary.11AcknowledgementsThe authors would like to acknowledge the incisive comments of Malcolm Atkinson, Peter Buneman and Rick Hull in the preparation of this document.This work was partially supported by Ministero della Pubblica Istruzione, Italy, the Science and Engineering Research Council, U.K. grant number GR/E 75395, NSF IRI 8606424 and the Office of Naval Research, University Research Initiative contract N00014 86-K-0764.12References[CW85]Cardelli L. and Wegner P., "On Understanding Types, Data Abstraction and Polymorphism",A.C.M. Computing Surveys, Vol. 17, No. 4 (December 1985), pp.471-522.[OO88]Proc. 2nd International Workshop on Object-Oriented Database Systems, West Germany. Lecture Notes in Computer Science, 334. Springer-Verlag, (September 1988).For detailed expositions of the issues discussed in this paper, the reader is referred to the following:Atkinson M.P. & Buneman O.P., "Types and Persistence in Database Programming Languages",A.C.M. Computing Surveys, Vol 19, No 2 (June 1987), pp.105-190.Banchilion F. & Buneman P. (Editors) Database Programming Languages. MIT Press.Cambridge Mass 1989.Atkinson M.P., Buneman O.P. & Morrison R. (Editors) Data Types and Persistence. Topicsin Information Systems Series, Springer-Verlag. Berlin 1988.Brodie M.L., Mylopoulos J. & Schmidt J.W. (Editors) On Conceptual Modelling. Topics inInformation Systems Series, Springer-Verlag. Berlin 1984.Danforth S. & Tomlinson C. "Type Theories and Object-Oriented Programming", A.C.M.Computing Surveys, Vol 20, No 1 (March 1988), pp.29-72.Dittrich K.R. (Editor) Advances in Object-Oriented Database Systems. Lecture Notes inComputer Science, Vol 334, Springer-Verlag, Berlin 1988.Shriver B. & Wegner P. (Editors) Research Directions in Object-Oriented Programming.Mit Press, Cambridge Mass. 1987.。
(面向对象设计)Part1Object-Oriented
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1.1. What Will You Learn? Is it Useful?
This book helps you:
▪ Apply principles and patterns to create better object designs.
▪ Iteratively follow a set of common activities in analysis and design.
UML 1.1
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Review Define object-oriented analysis and design
(OOA/D). Illustrate a brief OOA/D example. Overview UML and visual agile modeling
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1.6 What is the UML?
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程序设计语言教案英语
程序设计语言教案英语Title: Teaching Plan for Programming Language - EnglishIntroduction:This teaching plan aims to introduce students to the fundamentals of programming language using English as the medium of instruction. The plan is designed to cater to students at various educational stages and ensure their comprehension and practical application of programming concepts. By the end of this course, students should be able to understand and write basic programs using a programming language.Grade Level: Middle School (7th-9th grade)Objectives:1. Introduce students to the basic concepts of programming language in English.2. Familiarize students with the syntax and structure of a programming language.3. Develop students' problem-solving skills through programming exercises.4. Enhance students' ability to read and understand English technical documentation related to programming.Duration: 10 sessions (45 minutes per session)Session 1: Introduction to Programming- Introduce the concept of programming language and its importance in modern society.- Discuss the benefits and applications of learning a programming language.- Explain the role of English in programming and its significance in accessingglobal resources.Session 2: Programming Language Basics- Introduce students to the basic components of a programming language: variables, data types, and operators.- Explain the concept of control structures: conditional statements (if-else) and loops (for, while).- Provide examples and exercises to reinforce understanding.Session 3: Input and Output- Teach students how to take input from users and display output using programming language commands.- Discuss the importance of user-friendly interfaces and error handling.- Conduct practical exercises to reinforce learning.Session 4: Functions and Modules- Introduce the concept of functions and their role in code organization and reusability.- Explain the concept of modules and their significance in managing large-scale programs.- Provide examples and exercises to practice creating and using functions and modules.Session 5: Arrays and Lists- Introduce students to the concept of arrays and lists in programming.- Explain the benefits and applications of using arrays and lists.- Conduct exercises to practice manipulating arrays and lists.Session 6: File Handling- Teach students how to read from and write to files using programming language commands.- Discuss file formats and their significance in data storage and retrieval.- Conduct practical exercises to reinforce learning.Session 7: Debugging and Troubleshooting- Explain the importance of debugging in programming and introduce common debugging techniques.- Discuss common programming errors and their solutions.- Provide exercises to practice debugging skills.Session 8: Introduction to Object-Oriented Programming (OOP)- Introduce students to the concept of object-oriented programming.- Explain the basic principles of OOP: encapsulation, inheritance, and polymorphism.- Provide examples and exercises to reinforce understanding.Session 9: Project Development- Assign a small-scale programming project to students, allowing them to apply the concepts learned throughout the course.- Guide students through the project development process, providing assistance and feedback as needed.Session 10: Project Presentation and Assessment- Allow students to present their programming projects to the class.- Evaluate students' understanding and application of programming concepts. - Provide constructive feedback and suggestions for improvement. Assessment:- Regular quizzes and tests to assess students' understanding of programming concepts.- Evaluation of programming projects based on functionality, code quality, and adherence to programming principles.- Class participation and engagement during discussions and exercises. Note: This teaching plan can be adapted for different grade levels and adjusted based on the students' prior knowledge and language proficiency.。
面向对象分析英语作文
面向对象分析英语作文Title: The Power of Object-Oriented Analysis in English Composition。
In the realm of English composition, employing object-oriented analysis can significantly enhance the quality and coherence of one's writing. By breaking down complex ideas into manageable components and organizing them systematically, writers can create compelling and structured essays that effectively communicate their message. In this essay, we will explore the principles of object-oriented analysis and demonstrate its application in crafting high-quality English compositions.Object-oriented analysis is a systematic approach to problem-solving that focuses on identifying and defining objects, their attributes, and their relationships. In the context of English composition, objects can be thought of as the key elements or components of a topic or theme. These objects may include main ideas, supporting evidence,arguments, examples, and counterarguments. By analyzing these objects and their relationships, writers can develop a clear understanding of their subject matter and how best to present it to their audience.One of the fundamental principles of object-oriented analysis is abstraction, which involves focusing on the essential characteristics of an object while ignoring irrelevant details. In English composition, abstraction allows writers to distill complex concepts or argumentsinto concise and coherent statements. For example, when writing an essay on the importance of renewable energy, the writer may abstract the main idea into a statement such as "Renewable energy sources are essential for combating climate change and ensuring sustainable development." This abstraction captures the essence of the topic without getting bogged down in unnecessary details.Another principle of object-oriented analysis is encapsulation, which involves grouping related objects together and defining their interactions. In English composition, encapsulation allows writers to organize theirideas into coherent paragraphs or sections that flowlogically from one to the next. Each paragraph or section encapsulates a specific aspect of the topic, such as background information, arguments, evidence, or conclusions. By encapsulating related ideas together, writers can create a cohesive and structured narrative that guides the reader through their essay.Inheritance is another key principle of object-oriented analysis, which involves defining relationships between objects based on similarities and differences. In English composition, inheritance allows writers to build upon existing ideas or arguments and develop them further. For example, when writing an argumentative essay, the writer may inherit evidence or examples from previous paragraphsto support their claims. By leveraging inheritance, writers can create a sense of continuity and progression in their writing, leading to a more compelling and persuasive argument.Polymorphism is yet another principle of object-oriented analysis, which involves allowing objects to takeon different forms or behaviors depending on the context. In English composition, polymorphism allows writers to adapt their writing style and tone to suit the needs of their audience and the requirements of their genre. For example, when writing a formal academic essay, the writer may adopt a more scholarly tone and use specialized vocabulary to convey their ideas. In contrast, when writing a persuasive speech, the writer may use rhetorical devices and emotive language to engage and persuade their audience. By embracing polymorphism, writers can effectively communicate their message in a manner that resonates with their readers or listeners.To illustrate the application of object-oriented analysis in English composition, let us consider an example essay on the topic of technology and society. 。
英语思维养成指南 面向对象英语语法
英语思维养成指南面向对象英语语法全文共3篇示例，供读者参考篇1Title: A Guide to Developing Object-Oriented English Thinking - Object-Oriented English GrammarAbstract:English is a language that is deeply rooted in object-oriented thinking. Just as in programming, where objects are the building blocks of code, in English, objects are the building blocks of sentences. By understanding and mastering object-oriented English grammar, language learners can improve their fluency and communication skills. This guide will provide an in-depth look at how object-oriented thinking can be applied to English grammar, and offer practical tips for developing this mindset.Introduction:Object-oriented programming is a programming paradigm based on the concept of "objects", which can contain data in the form of fields, and code in the form of procedures. In a similar vein, object-oriented English grammar is centered around the concept of objects, which are the key elements in a sentence. Byviewing English grammar through an object-oriented lens, learners can better understand the relationships between different parts of a sentence, and enhance their ability to communicate effectively in English.Object-Oriented English Grammar:Nouns and pronouns are the primary objects in English grammar. Nouns are words that represent people, places, things, or ideas, while pronouns are words that can take the place of nouns. In object-oriented English grammar, nouns and pronouns serve as the central objects around which sentences are constructed. For example, in the sentence "She is reading a book", "She" is the subject pronoun, "book" is the object noun, and "is reading" is the action taking place.Verbs are the actions or states of being that are performed by the subject of a sentence. In object-oriented English grammar, verbs are closely linked to the objects they act upon. For example, in the sentence "He is eating an apple", "eating" is the verb and "apple" is the object that receives the action.Adjectives and adverbs are modifiers that provide additional information about nouns, pronouns, verbs, or other adjectives. In object-oriented English grammar, adjectives and adverbs are used to describe the objects in a sentence. For example, in thesentence "The big brown dog quickly ran across the field", "big" and "brown" are adjectives describing the noun "dog," and "quickly" is an adverb describing the verb "ran."Prepositions are words that show the relationship between a noun or pronoun and other words in a sentence. Inobject-oriented English grammar, prepositions are used to establish connections between objects. For example, in the sentence "The book is on the table," "on" is the preposition that links the object "book" to the object "table."Developing Object-Oriented Thinking in English:To develop object-oriented thinking in English, language learners can practice identifying and analyzing objects in sentences. By breaking down sentences into their constituent parts and understanding the relationships between objects, learners can improve their grasp of English grammar and syntax.One effective strategy for developing object-oriented thinking in English is to create mind maps or diagrams that visually represent the objects in a sentence and their relationships. By visually mapping out the structure of a sentence, learners can gain a better understanding of how objects interact with each other.Another strategy is to engage in activities that require learners to manipulate objects in sentences. For example, learners can practice changing the positions of objects in a sentence or substituting different objects to see how it affects the meaning of the sentence. By actively engaging with objects in sentences, learners can deepen their understanding of English grammar and syntax.Conclusion:Object-oriented English thinking is a valuable mindset for language learners to cultivate in order to improve their fluency and communication skills. By viewing English grammar through an object-oriented lens, learners can better understand the relationships between different parts of a sentence, and enhance their ability to express themselves effectively in English. By mastering object-oriented thinking in English, learners can take their language skills to new heights and communicate with clarity and precision.篇2Developing a Thinking in English Guide for Object-Oriented English GrammarIntroduction:English is a global language that is spoken by people all around the world. In order to communicate effectively in English, it is important to not only have a good grasp of the vocabulary and grammar rules but also to develop a thinking in English mindset. Object-oriented English grammar is a concept that can help learners better understand and internalize the rules of the language. In this guide, we will explore how to develop a thinking in English mindset using object-oriented English grammar.Understanding Object-Oriented English Grammar:Object-oriented English grammar is a method of teaching and learning English grammar that focuses on the relationships between different elements of a sentence. In object-oriented programming, objects interact with each other to perform various tasks. Similarly, in object-oriented English grammar, words and phrases in a sentence interact with each other to convey meaning.For example, in the sentence "John gave the book to Mary," "John" is the subject, "gave" is the verb, "the book" is the direct object, and "Mary" is the indirect object. By understanding the relationships between these elements, learners can better understand how sentences are constructed in English.Developing a Thinking in English Mindset:To develop a thinking in English mindset usingobject-oriented English grammar, learners can follow these steps:1. Identify the objects in a sentence:When analyzing a sentence, learners should identify the objects - including subjects, verbs, direct objects, indirect objects, and prepositional phrases. By breaking down the sentence into its constituent parts, learners can better understand how each element contributes to the overall meaning.2. Understand the relationships between objects:Once the objects in a sentence have been identified, learners should focus on understanding how these objects interact with each other. For example, in a sentence like "She gave me a present," the subject "She" is performing the action, the verb "gave" indicates the action, "me" is the indirect object, and "a present" is the direct object.3. Practice rearranging objects in a sentence:To deepen their understanding of object-oriented English grammar, learners can practice rearranging objects in a sentence. By changing the order of objects, learners can see how themeaning of the sentence shifts. For example, changing "John gave the book to Mary" to "Mary gave the book to John" alters the meaning of the sentence.4. Apply object-oriented English grammar to writing and speaking:Finally, learners should apply their knowledge ofobject-oriented English grammar to their own writing and speaking. By consciously thinking about the relationships between objects in sentences, learners can improve their communication skills and convey their ideas more effectively in English.Conclusion:Developing a thinking in English mindset usingobject-oriented English grammar can help learners better understand the rules of the language and communicate more effectively. By identifying objects in sentences, understanding their relationships, practicing rearranging objects, and applying object-oriented English grammar to writing and speaking, learners can develop a deeper grasp of English grammar and enhance their language skills. With dedication and practice, learners can cultivate a thinking in English mindset that will serve them well in their language learning journey.篇3English Thinking Development Guide: Object-Oriented English GrammarIn the realm of language learning, having a solid foundation in English grammar is essential for communicating effectively and comprehensively. One approach to mastering English grammar is through the concept of object-oriented programming, a programming paradigm where objects are the building blocks of software systems. By applying object-oriented principles to English grammar, learners can develop a systematic and structured understanding of the language, which can lead to enhanced comprehension and fluency.The key to mastering object-oriented English grammar lies in understanding the core concepts of object-oriented programming and applying them to language learning. In object-oriented programming, objects are self-contained units that encapsulate data and functionality. Similarly, in English grammar, objects are elements such as nouns, pronouns, and phrases that serve as the building blocks of sentences.To develop a solid grasp of object-oriented English grammar, learners should focus on the following principles:1. Encapsulation: In object-oriented programming, encapsulation refers to the bundling of data and functionality within an object. In English grammar, encapsulation can be seen in how words and phrases are grouped together to form coherent sentences. By understanding how words and phrases interact within a sentence, learners can grasp the concept of encapsulation in language.2. Inheritance: Inheritance is a key concept inobject-oriented programming, where objects can inherit properties and behaviors from other objects. In English grammar, inheritance can be seen in how words and phrases inherit grammatical properties from other elements in a sentence. By recognizing patterns of inheritance in language, learners can better understand how words and phrases are interconnected.3. Polymorphism: Polymorphism in object-oriented programming refers to the ability of objects to take on different forms and behaviors. In English grammar, polymorphism can be seen in how words and phrases can have multiple meanings and functions depending on their context. By recognizing the diverse ways in which words and phrases can be used, learners can develop a nuanced understanding of language.By applying the principles of object-oriented programming to English grammar, learners can develop a structured and systematic approach to language learning. By viewing language as a system of interconnected objects and relationships, learners can enhance their comprehension and fluency in English.In conclusion, mastering object-oriented English grammar requires a solid understanding of core programming principles and their application to language learning. By approaching language learning through the lens of object-oriented programming, learners can develop a structured and systematic understanding of English grammar, leading to improved communication skills and fluency.。
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Objects are independent units
• •
Object-oriented paradigm
• • •
Object-oriented analysis, design and develoct classes
Objects are entities in a software system which represent instances of real-world and system entities Object classes are templates for objects. They may be used to create objects Object classes may inherit attributes and services from other object classes
• • • Object classes are rectangles with the name at the top, attributes in the middle section and operations in the bottom section Relationships between object classes (known as associations) are shown as lines linking objects Inheritance is referred to as generalisation and is shown ‗upwards‘ rather than ‗downwards‘ in a hierarchy
• • • Inheritance models Aggregation models Interaction models
Object models
Natural ways of reflecting the real-world entities manipulated by the system More abstract entities are more difficult to model using this approach Object class identification is recognised as a difficult process requiring a deep understanding of the application domain Object classes reflecting domain entities are reusable across systems
Inheritance models
Organise the domain object classes into a hierarchy Classes at the top of the hierarchy reflect the common features of all classes Object classes inherit their attributes and services from one or more super-classes. these may then be specialised as necessary Class hierarchy design is a difficult process if duplication in different branches is to be avoided
Inheritance and OOD
There are differing views as to whether inheritance is fundamental to OOD.
• View 1. Identifying the inheritance hierarchy or network is a fundamental part of object-oriented design. Obviously this can only be implemented using an OOPL. View 2. Inheritance is a useful implementation concept which allows reuse of attribute and operation definitions. Identifying an inheritance hierarchy at the design stage places unnecessary restrictions on the implementation
Objects
An object is an entity which has a state and a defined set of operations which operate on that state. The state is represented as a set of object attributes. The operations associated with the object provide services to other objects (clients) which request these services when some computation is required. Objects are created according to some object class definition. An object class definition serves as a template for objects. It includes declarations of all the attributes and services which should be associated with an object of that class.
Object models describe the system in terms of object classes An object class is an abstraction over a set of objects with common attributes and the services (operations) provided by each object Various object models may be produced
Introduction to Object-Oriented Analysis and Design
Wang Jiening 2010-11-02
Object-Oriented Paradigm
Object consists of
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Data (attributes, state variables, instance variables, fields, data members), and Actions (methods, member functions) Conceptual independence Physical independence Reaction to perceived shortcomings in structured paradigm Problem of larger products Data and action treated as equal partners
Advantages of inheritance
It is an abstraction mechanism which may be used to classify entities It is a reuse mechanism at both the design and the programming level The inheritance graph is a source of organisational knowledge about domains and systems
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Inheritance introduces complexity and this is undesirable, especially in critical systems
The Unified Modeling Language
Several different notations for describing object-oriented designs were proposed in the 1980s and 1990s The Unified Modeling Language is an integration of these notations It describes notations for a number of different models that may be produced during OO analysis and design It is now a de facto standard for OO modelling Notation
Generalisation and inheritance
Objects are members of classes which define attribute types and operations Classes may be arranged in a class hierarchy where one class (a super-class) is a generalisation of one or more other classes (sub-classes) A sub-class inherits the attributes and operations from its super class and may add new methods or attributes of its own Generalisation in the UML is implemented as inheritance in OO programming languages