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Software Engineering Chapter 1 Introduction Ku-Yaw Chang Assistant Professor Department of Computer Science and Information Engineering.

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Presentation on theme: "Software Engineering Chapter 1 Introduction Ku-Yaw Chang Assistant Professor Department of Computer Science and Information Engineering."— Presentation transcript:

1 Software Engineering Chapter 1 Introduction Ku-Yaw Chang canseco@mail.dyu.edu.tw Assistant Professor Department of Computer Science and Information Engineering Da-Yeh University

2 2Ku-Yaw ChangSoftware Engineering Objectives Understand what software engineering is and why it is important Know the answers to key questions that provide an introduction to software engineering Understand some ethical and professional issues that are important for software engineers

3 3Ku-Yaw ChangSoftware Engineering Preamble Software engineering The economies of all developed nations are dependent on software The economies of all developed nations are dependent on software More and more systems are software controlled More and more systems are software controlled Software engineering is concerned with theories, methods and tools for professional software development Software engineering is concerned with theories, methods and tools for professional software development Expenditure on software represents a significant fraction of GNP in all developed countries Expenditure on software represents a significant fraction of GNP in all developed countries

4 4Ku-Yaw ChangSoftware Engineering Preamble Software cost Often dominate computer system costs Often dominate computer system costs The costs of software on a PC are often greater than the hardware cost Software costs more to maintain than it does to develop Software costs more to maintain than it does to develop For systems with a long life, maintenance costs may be several times development costs Software engineering is concerned with cost- effective software development.

5 5Ku-Yaw ChangSoftware Engineering Contents 1.1 FAQs about software engineering 1.2 Professional and ethical responsibility 1.3 Exercises

6 6Ku-Yaw ChangSoftware Engineering 1.1 FAQs about software engineering 1.What is software? What is software?What is software? 2.What is software engineering? What is software engineering?What is software engineering? 3.What is the difference between software engineering and computer science? What is the difference between software engineering and computer science?What is the difference between software engineering and computer science? 4.What is the difference between software engineering and system engineering? What is the difference between software engineering and system engineering?What is the difference between software engineering and system engineering? 5.What is a software process? What is a software process?What is a software process? 6.What is a software process model? What is a software process model?What is a software process model?

7 7Ku-Yaw ChangSoftware Engineering 1.1 FAQs about software engineering 7.What are the costs of software engineering? What are the costs of software engineering?What are the costs of software engineering? 8.What are software engineering methods? What are software engineering methods?What are software engineering methods? 9.What is CASE (Computer-Aided Software Engineering)? What is CASE (Computer-Aided Software Engineering)?What is CASE (Computer-Aided Software Engineering)? 10.What are the attributes of good software? What are the attributes of good software?What are the attributes of good software? 11.What are the key challenges facing software engineering? What are the key challenges facing software engineering?What are the key challenges facing software engineering?

8 8Ku-Yaw ChangSoftware Engineering 1.1.1 What is software? Computer programs and associated documentation such as requirements, design models and user manuals. Software products may be developed for a particular customer or may be developed for a general market. Software products may be Generic - developed to be sold to a range of different customers e.g. PC software such as Excel or Word. Generic - developed to be sold to a range of different customers e.g. PC software such as Excel or Word. Customized (Bespoke) - developed for a single customer according to their specification. Customized (Bespoke) - developed for a single customer according to their specification. New software can be created by developing new programs, configuring generic software systems or reusing existing software. FAQs

9 9Ku-Yaw ChangSoftware Engineering 1.1.2 What is software engineering? An engineering discipline that is concerned with all aspects of software production from the early stages of system specification to maintaining the system after it has gone into use. Engineering discipline Engineering discipline Apply theories, methods and tools to discover solutions Work to organizational and financial constraints All aspects of software production All aspects of software production Technical processes Project management Developments of tools, methods and theories FAQs

10 10Ku-Yaw ChangSoftware Engineering 1.1.3 What is the difference between software engineering and computer science? Computer science Be concerned with theories and methods that underlie computers and software systems Be concerned with theories and methods that underlie computers and software systems Software engineering Be concerned with the practical problems of producing software Be concerned with the practical problems of producing software  Computer science theories are still insufficient to act as a complete underpinning for software engineering (unlike e.g. physics and electrical engineering). FAQs

11 11Ku-Yaw ChangSoftware Engineering 1.1.4 What is the difference between software engineering and system engineering? System engineering Be concerned with all aspects of computer-based systems development Be concerned with all aspects of computer-based systems development including hardware, software and process engineering including hardware, software and process engineering Software engineering Be concerned with developing the software infrastructure, control, applications and databases in the system. Be concerned with developing the software infrastructure, control, applications and databases in the system. part of system engineering  System engineers are involved in system specification, architectural design, integration and deployment. FAQs

12 12Ku-Yaw ChangSoftware Engineering 1.1.5 What is a software process? A set of activities and associated results that produce a software product Generic activities in all software processes are: Specification - what the system should do and its development constraints Specification - what the system should do and its development constraints Development - production of the software system Development - production of the software system Validation - checking that the software is what the customer wants Validation - checking that the software is what the customer wants Evolution - changing the software in response to changing demands Evolution - changing the software in response to changing demands FAQs

13 13Ku-Yaw ChangSoftware Engineering 1.1.6 What is a software process model? A simplified representation of a software process, presented from a specific perspective Examples of process perspectives are Workflow perspective Workflow perspective Sequence of activities; human actions Dataflow perspective Dataflow perspective A set of activities carrying out data transformation By people or computers Role/action perspective Role/action perspective Who does what Generic process models Waterfall approach Waterfall approach Iterative development Iterative development Component-based software engineering (CBSE) Component-based software engineering (CBSE) FAQs

14 14Ku-Yaw ChangSoftware Engineering 1.1.7 What are the costs of software engineering? Roughly 60% of costs are development costs, 40% are testing costs. For custom software, evolution costs often exceed development costs. For custom software, evolution costs often exceed development costs. Costs vary 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.

15 15Ku-Yaw ChangSoftware Engineering Activity cost distribution

16 16Ku-Yaw ChangSoftware Engineering Product development costs FAQs

17 17Ku-Yaw ChangSoftware Engineering 1.1.8 What are software engineering methods? Structured approaches to software development To facilitate the production of high-quality software in a cost- effective way To facilitate the production of high-quality software in a cost- effective wayExamples Function-Oriented Function-Oriented Structured Analysis (DeMarco, 1978) JSD (Jackson, 1983) Object-Oriented Object-Oriented Unified Approach built around the Unified Modeling Language (UML) Integrating Booch (Booch, 1994) and Rmbaugh (Rambaugh, 1991) Integrating Booch (Booch, 1994) and Rmbaugh (Rambaugh, 1991) No ideal method Different methods are applicable to different areas Different methods are applicable to different areas OO methods are not suitable for real-time requirements

18 18Ku-Yaw ChangSoftware Engineering 1.1.8 What are software engineering methods? Method components Model descriptions Model descriptions Descriptions of graphical models which should be produced e.g. object models, data-flow models Rules Rules Constraints applied to system models e.g. Entity must have a unique name. Recommendations Recommendations Advice on good design practice e.g. No more than seven sub-objects associated with it. Process guidance Process guidance What activities to follow e.g. Document attributes before defining the operations. FAQs

19 19Ku-Yaw ChangSoftware Engineering 1.1.9 What is CASE? CASE: Computer Aided Software Engineering Software systems that are intended to provide automated support for software process activities Software systems that are intended to provide automated support for software process activities Often used for method support Often used for method supportUpper-CASE Tools to support the early process activities of requirements and design Tools to support the early process activities of requirements and designLower-CASE Tools to support later activities such as programming, debugging and testing Tools to support later activities such as programming, debugging and testing FAQs

20 20Ku-Yaw ChangSoftware Engineering 1.1.10 What are the attributes of good software? Software products Services (functional) Services (functional) Other attributes reflecting its quality (non-functional) Other attributes reflecting its quality (non-functional) e.g. response time, understandability of the code A special set of attributes depends on its application A banking system must be secure An interactive game must be responsive A telephone switching system must be reliable

21 21Ku-Yaw ChangSoftware Engineering Essential attributes of good software Maintainability Evolve to meet changing needs Evolve to meet changing needsDependability Be trustworthy Be trustworthy Reliability, security, and safety Efficiency Make no wasteful use of system resources Make no wasteful use of system resources Responsiveness, processing time, memory utilization, etc. Usability Be usable Be usable Appropriate user interface and adequate documentation FAQs

22 22Ku-Yaw ChangSoftware Engineering 1.1.11 What are the key challenges facing software engineering? Heterogeneity Developing techniques for building software that can cope with heterogeneous platforms and execution environments Developing techniques for building software that can cope with heterogeneous platforms and execution environmentsDelivery Developing techniques that lead to faster delivery of software Developing techniques that lead to faster delivery of softwareTrust Developing techniques that demonstrate that software can be trusted by its users Developing techniques that demonstrate that software can be trusted by its users FAQs

23 23Ku-Yaw ChangSoftware Engineering Contents 1.1 FAQs about software engineering 1.2 Professional and ethical responsibility 1.3 Exercises

24 24Ku-Yaw ChangSoftware Engineering 1.2 Professional and ethical responsibility Software engineering involves wider responsibilities than simply the application of technical skills. Software engineers must behave in an honest and ethically responsible way if they are to be respected as professionals. Ethical behavior is more than simply upholding the law.

25 25Ku-Yaw ChangSoftware Engineering Issues of professional responsibility (I) Confidentiality Engineers should normally respect the confidentiality of their employers or clients irrespective of whether or not a formal confidentiality agreement has been signed. Engineers should normally respect the confidentiality of their employers or clients irrespective of whether or not a formal confidentiality agreement has been signed.Competence Engineers should not misrepresent their level of competence. They should not knowingly accept work which is outside their competence. Engineers should not misrepresent their level of competence. They should not knowingly accept work which is outside their competence.

26 26Ku-Yaw ChangSoftware Engineering Issues of professional responsibility (II) Intellectual property rights 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. 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 Software engineers should not use their technical skills to misuse other people’s computers. Computer misuse ranges from relatively trivial (game playing on an employer’s machine, say) to extremely serious (dissemination of viruses). Software engineers should not use their technical skills to misuse other people’s computers. Computer misuse ranges from relatively trivial (game playing on an employer’s machine, say) to extremely serious (dissemination of viruses).

27 27Ku-Yaw ChangSoftware Engineering Code of Ethics The professional societies have cooperated to produce a code of ethical practice. ACM ACM IEEE (Institute of Electrical and Electronic Engineers) IEEE (Institute of Electrical and Electronic Engineers) British Computer Society British Computer Society Members of these organizations sign up to the code of practice when they join. The Code contains eight Principles related to the behavior of and decisions made by professional software engineers, including practitioners, educators, managers, supervisors and policy makers, as well as trainees and students of the profession.

28 28Ku-Yaw ChangSoftware Engineering Eight principles (I) PUBLIC Software engineers shall act consistently with the public interest. Software engineers shall act consistently with the public interest. CLIENT AND EMPLOYER Software engineers shall act in a manner that is in the best interests of their client and employer consistent with the public interest. Software engineers shall act in a manner that is in the best interests of their client and employer consistent with the public interest.PRODUCT Software engineers shall ensure that their products and related modifications meet the highest professional standards possible. Software engineers shall ensure that their products and related modifications meet the highest professional standards possible.

29 29Ku-Yaw ChangSoftware Engineering Eight principles (II) JUDGMENT Software engineers shall maintain integrity and independence in their professional judgment. Software engineers shall maintain integrity and independence in their professional judgment.MANAGEMENT Software engineering managers and leaders shall subscribe to and promote an ethical approach to the management of software development and maintenance. Software engineering managers and leaders shall subscribe to and promote an ethical approach to the management of software development and maintenance.PROFESSION Software engineers shall advance the integrity and reputation of the profession consistent with the public interest. Software engineers shall advance the integrity and reputation of the profession consistent with the public interest.

30 30Ku-Yaw ChangSoftware Engineering Eight principles (III) COLLEAGUES Software engineers shall be fair to and supportive of their colleagues. Software engineers shall be fair to and supportive of their colleagues.SELF 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. 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.

31 31Ku-Yaw ChangSoftware Engineering Ethical dilemmas Disagreement in principle with the policies of senior management. Your employer acts in an unethical way and releases a safety-critical system without finishing the testing of the system. Participation in the development of military weapons systems or nuclear systems.

32 32Ku-Yaw ChangSoftware Engineering Contents 1.1 FAQs about software engineering 1.2 Professional and ethical responsibility 1.3 Exercises

33 33Ku-Yaw ChangSoftware Engineering 1.3 Exercises 1.61.71.8

34 The End


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