软件工程知识点

1、1,软件工程为什么产生？ Born in 1968, Because of Software Crisis （high costs, slow delivery, low quality）什么是软件？Computer programs and associated documentation and Configuration Data程序、相关文档和 数据软件：定制通用什么是软件工程？Software engineering is an engineering discipline which is concerned with all aspects of software product

2、ion （涉及软件所有方面的工程原则）什么是软件过程？A set of activities whose goal is the development or evolution of software什么是软件工程模型？辅助工具（高端工具，低端工具）Software systems which are intended to provide automated support for software process activities. CASE systems are often used for method supportUpper-CASE （高端工具）Tools to supp

3、ort the early process activities of requirements and designLower-CASE （低端工具）Tools to support later activities such as programming, debugging and testing8优良软件特性（可维护，可信赖，有效）Maintainability （可维护）Dependability （可信赖）Efficiency （有效）Usability （可用）面临挑战（遗留系统，多样性，交付）Legacy systems （遗留系统）Old, valuable systems

4、must be maintained and updatedHeterogeneity （多样性）Systems are distributed and include a mix of hardware and softwareDelivery （交付）There is increasing pressure for faster delivery of software职业道德（机密，工作竞争力，知识产权，计算机滥用）Confidentiality （机密）Competence （工作竞争力）Intellectual property rights （知识产权）Computer misus

5、e （计算机滥用）一般软件过程模型（4种）The waterfall model（瀑布模型）Evolutionary development（进化式模型）Formal systems development（形式化模型）Reuse-based development（面向复用模型）（1）瀑布模型的内容、问题内容:requirements define ,system and software design, implementation and unittesting , integration and system testing , operation and miantainance 问

6、题：Inflexible partitioning of the project into distinct stages （僵化的阶段划分）This makes it difficult to respond to changing customer requirements （不适应需 求变化）Therefore, this model is only appropriate when the requirements are well-understood （适用于需求明确的系统）（2）进化开发（深化开发、抛弃开发问题）Exploratory development （演化开发）Obje

7、ctive is to work with customers and to evolve a final system from an initial outline specification. Should start with well-understood requirementsThrow-away prototyping （抛弃开发）Objective is to understand the system requirements. Should start with poorly understood requirementsProblems （问题）Lack of proc

8、ess visibility （过程不可见）Systems are often poorly structured （系统结构不好）Special skills （e.g. in languages for rapid prototyping） may be required （需要一 些技巧）计算机辅助工具（工具、工作平台、环境）Tools （工具）Support individual process tasks such as design consistency checking, text editing, etc.Workbenches （工作平台）Support a process

9、 phase such as specification or design, Normally include a number of integrated toolsEnvironments （环境）Support all or a substantial part of an entire software process. Normally include several integrated workbenches需求类型：用户需求、系统需求、软件设计描述User requirements 用户需求Statements in natural language plus diagram

10、s of the services the system provides and itsoperational constraints. Written for customersSystem requirements 系统需求A structured document setting out detailed descriptions of the system services. Written as a contract between client and contractorSoftware specification 软件设计描述A detailed software descr

11、iption which can serve as a basis for a design or implementation.Written for developers功能需求和非功能需求Functional requirements 功能需求Statements of services the system should provide, how the system should react to particular inputs and how the system should behave in particular situations.Non-fUnctional req

12、uirements 非功能需求constraints on the services or functions offered by the system such as timing constraints, constraints on the development process, standards, etc.Domain requirements 领域需求Requirements that come from the application domain of the system and that reflect characteristics of that domain5 自

13、然语言的问题（Problems with natural language）Lack of clarity 描述不精确Precision is difficult without making the document difficult to readRequirements confusion 需求混舌LFunctional and non-functional requirements tend to be mixed-upRequirements amalgamation 需求混合Several different requirements may be expressed toget

14、her6快速原型分析（好处）Advantage:Improved system usabilityCloser match to the system neededImproved design qualityImproved maintainabilityReduced overall development effort界面：交互方式（5种）Direct manipulation直接操作Menu selection菜单选择Form fill-in表格填写Command language命令语言Natural language自然语言设计原则16User familiarity 用户熟悉 C

15、onsistency 一致性Minimal surprise 不意外Recoverability可撤消 User guidance用户指导User diversity用户多样性:残疾人校验对比有效性验证Verification:Are we building the product rightThe software should conform to its specificationValidation:Are we building the right productThe software should do what the user really requires测试过程：单元测试

16、Unit testing 单元测试Component testing 构件测试System testing 集成测试Release testing 发布测试测试方法：1.黑盒法(不看代码)An approach to testing where the program is considered as a black-box The program test cases are based on the system specification Test planning can begin early in the software process2.白盒法(看代码的程序关系图)缺陷测试Th

17、e goal of defect testing is to discover defects in programsA successfufefect test is a test which causes a program to behave in an anomalous way Tests show the presence not the absence of defects等价类划分Input data and output results often fall into different classes where all members of a class are rel

18、atedEach of these classes is an equivalence partition where the program behaves in an equivalent way for each class memberTest cases should be chosen from each partition成本构成(Software cost components)Hardware and software costsTravel and training costsEffort costs (the dominant factor in most project

19、s)salaries of engineers involved in the projectSocial and insurance costsEffort costs must take overheads into accountcosts of building, heating, lightingcosts of networking and communicationscosts of shared facilities （e.g library, staff restaurant, etc.）估计方法Algorithmic cost modellingExpert judgeme

20、ntEstimation by analogyParkinsons LawPricing to win什么是质量Quality, simplistically, means that a product should meet its specification质量特性软件改变（不可避免）Software change is inevitable （软件改变不可避免）New requirements emerge when the software is usedThe business environment changesErrors must be repairedNew equipment