《软件工程》课件(全).pptx

1、Software Engineering,Born in 1968, Because of Software Crisis(high costs, slow delivery, low quality),Bilingual language teaching,双语教学（中英，中俄，中韩） 板书、讲授、作业、考试采用两种语言的混杂，比例是外语不低于20% 是基础英语、科技英语、专业英语的延续，体现英语教学的不断线。 是英语的应用，不是为了学习英语，经过近20年的英语学习，现在是大家应用英语的时候了。 双语软件工程是为了学习软件工程的知识，是为了达到国际水平而开设的。,State investig

2、ate,Program language： 1.会C语言 2.除C语言外，会C+ 3.还会Java, C# Practices： 1.生成过exe文件 2.制作过setup文件 3.做过网站,State investigate,听说过： 1.软件工程 2.瀑布型模型 3.构件 4.OCX，DLL，COM，J2EE 5.SOA 6.云计算,Purpose,教我们如何做软件，按照工程化的方法开发软件,What is software?（什么是软件）,Computer programs and associated documentation and Configuration Data 程序、相关

3、文档和数据 Software products may be developed for a particular customer or may be developed for a general market 订制和通用,What is software engineering?（什么是软件工程）,Software engineering is an engineering discipline which is concerned with all aspects of software production（涉及软件所有方面的工程原则） Software engineers shou

4、ld adopt a systematic and organised approach to their work and use appropriate tools and techniques depending on the problem to be solved, the development constraints and the resources available （采用系统方法、工具和管理技术）,What is the difference between software engineering and computer science?,Computer scien

5、ce is concerned with theory and fundamentals; software engineering is concerned with the practicalities of developing and delivering useful software Computer science theories are currently insufficient to act as a complete underpinning for software engineering 计算机科学是基础理论，支撑软件工程,What is the differenc

6、e between software engineering and system engineering?,System engineering is concerned with all aspects of computer-based systems development including hardware, software and process engineering. Software engineering is part of this process System engineers are involved in system specification, arch

7、itectural design, integration and deployment 软件工程是系统工程的分支,What is a software process?（什么是软件过程）,A set of activities whose goal is the development or evolution of software Generic activities in all software processes are: Specification 、Development 、Validation 、Evolution 软件开发和升级的一系列活动：描述、开发、测试和升级,What

8、 is a software process model?（什么是软件过程模型）,A simplified representation of a software process, presented from a specific perspective（简单概括） Examples of process perspectives are Workflow perspective（工作流） Data-flow perspective （信息流） Role/action perspective （角色/行为） Generic process models Waterfall（瀑布型） Evo

9、lutionary development（进化型） Formal transformation（形式化型） Integration from reusable components（面向复用型）,What are the costs of software engineering?（什么是软件工程成本）,Roughly 60% of costs are development costs, 40% are testing costs. For custom software, evolution costs often exceed development costs Costs vary

10、depending on the type of system being developed and the requirements of system attributes such as performance and system reliability Distribution of costs depends on the development model that is used,What are software engineering methods?（什么是软件工程方法）,Structured approaches to software development whi

11、ch include system models, notations, rules, design advice and process guidance Model descriptions（模型描述） Descriptions of graphical models which should be produced Rules（规则） Constraints applied to system models Recommendations（建议） Advice on good design practice Process guidance（过程指南） What activities t

12、o follow,What is CASE (Computer-Aided Software Engineering)（辅助工具）,Software systems which are intended to provide automated support for software process activities. CASE systems are often used for method support Upper-CASE（高端工具） Tools to support the early process activities of requirements and design

13、 Lower-CASE（低端工具） Tools to support later activities such as programming, debugging and testing,What are the attributes of good software?（优良软件的特性是什么？）,The software should deliver the required functionality and performance to the user and should be maintainable, dependable and usable Maintainability（可

14、维护） Dependability（可信赖） Efficiency（有效） Usability（可用）,What are the key challenges facing software engineering?（面临的挑战）,Coping with legacy systems, coping with increasing diversity and coping with demands for reduced delivery times Legacy systems（遗留系统） Old, valuable systems must be maintained and update

15、d Heterogeneity（多样性） Systems are distributed and include a mix of hardware and software Delivery（交付） There is increasing pressure for faster delivery of software,Issues of professional responsibility（职业道德）,Confidentiality （机密） Engineers should normally respect the confidentiality of their employers

16、or clients irrespective of whether or not a formal confidentiality agreement has been signed. Competence （工作竞争力） Engineers should not misrepresent their level of competence. They should not knowingly accept work which is out with their competence.,Issues of professional responsibility （职业道德）,Intelle

17、ctual property rights （知识产权） Engineers should be aware of local laws governing the use of intellectual property such as patents, copyright, etc. They should be careful to ensure that the intellectual property of employers and clients is protected. Computer misuse （计算机滥用） Software engineers should no

18、t use their technical skills to misuse other peoples computers. Computer misuse ranges from relatively trivial (game playing on an employers machine, say) to extremely serious (dissemination of viruses).,Code of ethics principles （代码道德）,1. PUBLIC（公众感） Software engineers shall act consistently with t

19、he public interest. 2. CLIENT AND EMPLOYER （客户和顾主） Software engineers shall act in a manner that is in the best interests of their client and employer consistent with the public interest. 3. PRODUCT （产品） Software engineers shall ensure that their products and related modifications meet the highest p

20、rofessional standards possible.,Code of ethics principles （代码道德）,JUDGMENT （判断力） Software engineers shall maintain integrity and independence in their professional judgment. 5. MANAGEMENT （管理能力） Software engineering managers and leaders shall subscribe to and promote an ethical approach to the manage

21、ment of software development and maintenance. 6. PROFESSION （职业感） Software engineers shall advance the integrity and reputation of the profession consistent with the public interest.,Code of ethics principles （代码道德）,7. COLLEAGUES （对待同事） Software engineers shall be fair to and supportive of their col

22、leagues. 8. SELF （自我要求） Software engineers shall participate in lifelong learning regarding the practice of their profession and shall promote an ethical approach to the practice of the profession.,Key points(主要知识点),Software engineering is an engineering discipline which is concerned with all aspect

23、s of software production. Software products consist of developed programs and associated documentation. Essential product attributes are maintainability, dependability, efficiency and usability. The software process consists of activities which are involved in developing software products. Basic act

24、ivities are software specification, development, validation and evolution.,Key points,CASE tools are software systems which are designed to support routine activities in the software process such as editing design diagrams, checking diagram consistency and keeping track of program tests which have b

25、een run. Software engineers have responsibilities to the engineering profession and society. They should not simply be concerned with technical issues. Professional societies publish codes of conduct which set out the standards of behaviour expected of their members.,Homework,what is software? what

26、is Software Engineering? what is software process? what are the costs of Software Engineering? what is CASE? what is software engineering code of ethics and professional practice?,Software Processes (软件过程),Coherent sets of activities for specifying, designing, implementing and testing software syste

27、ms （定义、设计、实现和测试等一系列活动）,Generic software process models（一般软件过程模型）,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）,Waterfall model（瀑布模型）,需求定义,系统和软件设计,编码和单元测试,集成和系统测试,运行和维护,Waterfall model problems（瀑布模型的问题）,Inflexible parti

28、tioning 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）,Evolutionary development（进化开发）,Exploratory development （演化开发） Objective

29、is to work with customers and to evolve a final system from an initial outline specification. Should start with well-understood requirements Throw-away prototyping（抛弃开发） Objective is to understand the system requirements. Should start with poorly understood requirements,Evolutionary development （进化开

30、发）,Evolutionary development （进化开发）,Problems（问题） Lack of process 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） Applicability（适用于） For small or medium-size interactive systems 中等规模的交互系统 For parts of large

31、systems (e.g. the user interface) 大系统的一部分 For short-lifetime systems 生命周期短的系统,Formal systems development（形式化系统开发）,Based on the transformation of a mathematical specification through different representations to an executable program （基于数学模型） Transformations are correctness-preserving so it is straig

32、htforward to show that the program conforms to its specification （正确转换） Embodied in the Cleanroom approach to software development（净室方法）,Formal systems development （形式化系统开发）,需求定义,形式化描述,形式化转换,集成和系统测试,Formal transformations （形式化转换）,形式描述,可执行系统,Formal systems development （形式化系统开发）,Problems（问题） Need for

33、specialised skills and training to apply the technique Difficult to formally specify some aspects of the system such as the user interface Applicability（适用于） Critical systems especially those where a safety or security case must be made before the system is put into operation,Reuse-oriented developm

34、ent（面向复用的开发）,Based on systematic reuse where systems are integrated from existing components or COTS (Commercial-off-the-shelf) systems（现成商业系统） Process stages Component analysis（构件分析） Requirements modification（需求修改） System design with reuse（系统设计） Development and integration（开发和集成） This approach is b

35、ecoming more important but still limited experience with it,Reuse-oriented development （面向复用的开发）,需求定义,构件分析,需求调整,系统设计,设计和集成,系统测试,Process iteration（过程反复）,System requirements ALWAYS evolve in the course of a project so process iteration where earlier stages are reworked is always part of the process fo

36、r large systems Iteration can be applied to any of the generic process models Two (related) approaches Incremental development Spiral development,Incremental development（增量开发）,Rather than deliver the system as a single delivery, the development and delivery is broken down into increments with each i

37、ncrement delivering part of the required functionality User requirements are prioritised and the highest priority requirements are included in early increments Once the development of an increment is started, the requirements are frozen though requirements for later increments can continue to evolve

38、,Spiral development（螺旋开发）,Process is represented as a spiral rather than as a sequence of activities with backtracking Each loop in the spiral represents a phase in the process. No fixed phases such as specification or design - loops in the spiral are chosen depending on what is required Risks are e

39、xplicitly assessed and resolved throughout the process,Spiral model of the software process （螺旋开发）,总结,进化式模型是新手和新的不熟悉项目的首选 瀑布模型有经验的人对熟悉的系统 形式化转换往往针对协议一类便于形式化的系统 面向复用是成功的商业系统 现在软件开发面临： 1.平台的不同 2.工具的不同,Automated process support (CASE)（计算机辅助工具）,Computer-aided software engineering (CASE) is software to s

40、upport software development and evolution processes Activity automation（自动化） Graphical editors for system model development Data dictionary to manage design entities Graphical UI builder for user interface construction Debuggers to support program fault finding Automated translators to generate new

41、versions of a program,Case technology （计算机辅助工具技术）,Case technology has led to significant improvements in the software process though not the order of magnitude improvements that were once predicted（工具作用尚未达到预期） Software engineering requires creative thought - this is not readily automatable（创造性行为） So

42、ftware engineering is a team activity and, for large projects, much time is spent in team interactions. CASE technology does not really support these （人之间交互太多）,CASE classification （计算机辅助工具分类）,Classification helps us understand the different types of CASE tools and their support for process activitie

43、s Functional perspective(功能观点） Tools are classified according to their specific function Process perspective（过程观点） Tools are classified according to process activities that are supported Integration perspective（集成观点） Tools are classified according to their organisation into integrated units,CASE int

44、egration （计算机辅助工具集成）,Tools（工具） Support individual process tasks such as design consistency checking, text editing, etc. Workbenches（工作平台） Support a process phase such as specification or design, Normally include a number of integrated tools Environments（环境） Support all or a substantial part of an en

45、tire software process. Normally include several integrated workbenches,Key points（主要知识点）,Software processes are the activities involved in producing and evolving a software system. They are represented in a software process model General activities are specification, design and implementation, valid

46、ation and evolution Generic process models describe the organisation of software processes Iterative process models describe the software process as a cycle of activities,Key points （主要知识点）,Requirements engineering is the process of developing a software specification Design and implementation proce

47、sses transform the specification to an executable program Validation involves checking that the system meets to its specification and user needs Evolution is concerned with modifying the system after it is in use CASE technology supports software process activities,1.what are the four software proce

48、ss models? 2.what is the waterfall model? Advantages and disadvantages? 3. what are the two kind models of evolutionary model? Advantages and disadvantages? 4.what is the reuse-based model? Advantages and disadvantages? 5.what is formal system development model? Advantages and disadvantages?,Homewor

49、k,Project management项目管理,Organising, planning and scheduling software projects 软件项目的组织、计划和进度安排,角色模拟,假设马鞍山股份钢铁公司投资1亿元人民币，开发全公司的ERP(Enterprise Resource Planning)管理系统,你作为项目负责人，请问你如何开展工作，写出提纲。,给出参考,项目规划和计划 人员组成 进度安排 成本预算（经费分配） 风险管理,Topics covered包含主要内容,Management activities 管理行为 Project planning 计划管理 Pr

50、oject scheduling 进度管理 Risk management 风险管理,The product is intangible 不可见性 The product is uniquely flexible 弹性 Software engineering is not recognized as an engineering discipline with the same status as mechanical, electrical engineering, etc. The software development process is not standardised 无标准

51、Many software projects are one-off projects 一次性,Software management distinctions软件管理特点,Project staffing人员管理,May not be possible to appoint the ideal people to work on a project Project budget may not allow for the use of highly-paid staff Staff with the appropriate experience may not be available An

52、 organisation may wish to develop employee skills on a software project Managers have to work within these constraints especially when (as is currently the case) there is an international shortage of skilled IT staff,Project plan structure项目计划结构,Introduction Project organisation Risk analysis Hardwa

53、re and software resource requirements Work breakdown Project schedule Monitoring and reporting mechanisms,Milestones in the RE process软件工程中的里程碑,Project scheduling项目进度,Split project into tasks and estimate time and resources required to complete each task Organize tasks concurrently to make optimal u

54、se of workforce Minimize task dependencies to avoid delays caused by one task waiting for another to complete Dependent on project managers intuition and experience,Scheduling problems进度问题,Estimating the difficulty of problems and hence the cost of developing a solution is hard Productivity is not p

55、roportional to the number of people working on a task Adding people to a late project makes it later because of communication overheads The unexpected always happens. Always allow contingency in planning,Bar charts and activity networks横道图和活动网络,Graphical notations used to illustrate the project sche

56、dule Show project breakdown into tasks. Tasks should not be too small. They should take about a week or two Activity charts show task dependencies and the the critical path Bar charts show schedule against calendar time,Task durations and dependencies,Activity network活动网络,Activity timeline横道图,Staff

57、allocation人员分配,Risk management风险管理,Risk management is concerned with identifying risks and drawing up plans to minimise their effect on a project. A risk is a probability that some adverse circumstance will occur. Project risks affect schedule or resources Product risks affect the quality or perform

58、ance of the software being developed Business risks affect the organisation developing or procuring the software,The risk management process风险管理过程,Risk identification Identify project, product and business risks Risk analysis Assess the likelihood and consequences of these risks Risk planning Draw u

59、p plans to avoid or minimise the effects of the risk Risk monitoring Monitor the risks throughout the project,Risk identification风险识别,Technology risks 技术风险 People risks 人员风险 Organisational risks 机构风险 Requirements risks 需求风险 Estimation risks 估算风险,Risk analysis风险分析,Assess probability and seriousness of each risk Probability may be very low, low, moderate, high or very high 风险的可能性大小 Risk effects might be catastrophic, serious, tolerable or insignificant 风险影响大小,Risk planning风险规划,Consider each risk and develop a strategy to manage that risk Avoidance strategies 避免风险 Th