Software

What is Software?

[Program <= Software]

• Program: A collection of istructions

• Software: Not only programs (codes), but all associatd documentation
  

[Software In Academia]
ICSE (International Conference on Software Engineering)
-> The premier software engineering conference in the world.

1. A README file: A main file describing what the software does.

2. A REQUIREDMENTS file: This file should cover aspects of hardware environment requirements and software environments.

3. A LICENSE file: the file describing the distribution rights.

4. An INSTALL file: These installation istructions should include notes illustrating a very basic usage example or a method to test the installation.

Software Costs

• Software costs more to maintain than it does to develop. (maintenance cost가 더 비쌈!)
  • Debugging takes up half of the time in SW development. (debugging이 개발 단계에서 절반 차지)

SW Project Failure Reason

• Increasing system complexity

  • The size of software is increasing rapidly.

• Failure to use software engineering methods (software engineering methods를 쓰지 않아서)

  • It is fairly easy for people (including me) to write computer programs without using software engineering methods and techniques.

Software Engineering

Software Engineering

[Software engineering]

• An engineering discipline that is concerned with from the early stages of system specification all aspects of software production through to maintaining the system after it has gone into use.
  

[Engineering discipline]

• Using appropriate theories and methods to solve problems bearing in mind organizational and financial constraints.

[All aspects of software production]

• Not just technical process of development.
• Also, project management and the development of tools, methods

[Topics in Software engineering]

• AI and software engineering

  • Machine learning with and for SE, Program synthesis, Program repair

• Testing and anlaysis

  • Software testing, Program analysis, Debugging and Fault localization

• Software evolution

  • Evolution and maintenance, Software reuse, Refactoring

• Social aspects of software engineering

  • Agile methods and software processes, Ethics in software engineering

• Requirements, modeling, and design

  • Requirements engineering, Modeling and model-driven engineering

Importance of SW engineering

• Dependency of Software

  • More and more, individuals and society rely on complex software systems.
  • We need to be able to produce reliable and trustworthy systems economically and quickly.

• Cost Saving

  • It is usually cheaper, in the long run, to use software engineering methods and techniques for software systems rather than just write the programs as if it was a personal programming project.
  • For most types of system, most costs are the costs of changing the software after it has gone into use.

About Developing SW

Software Process Activities

• Software Specification

  • where customers and engineers define the software that is to be produced and the constraints on its operation.

• Software Development

  • where the software is designed and programmed.

• Software Validation

  • where the software is checked to ensure that it is what the customer requires.

• Software Evolution

  • where the software is modified to reflect changing customer and market requirements.

General Issues that Affect SW

• Heterogeneity (이질)

  • Increasingly, systems are required to operate as distributed systems across networks that include different types of computer and mobile devices.

• Business and social change

  • Buisiness and society are changing incredibly quickly as emerging economies develop and new technologies become available.
  • They need to be able to change their existing software and to rapidly develop new software.

• Security and trust

  • As software is intertwined(얽혀) with all aspects of our lives, it is essential that we can trust that software.

Details of SW Engineering

Question to understand SE

[What is software?]

• Computer programs and associated documentation.

[What are the attributes of good software?]

• Good software should deliver the required functionality and performance to the user and should be maintainable, dependable and usable.

[What is software engineering?]

• Software engineering is an engineering discipline that is concerned with all aspects of software production.

[What are the fundamental software engineering activities?]

• Software specification, software development, software validation and software evolution.

• s -> d -> v -> e

[What are the key challenges facing software engineering?]

• Coping with increasing diversity, demands for reduced delivery times and developing trustworthy software.

[What are the costs of software engineering?]

• Roughly 60% of software costs are development costs, 40% are testing cost.

• For custom software, evolution costs often exceed development costs.

[What are the best software engineering techniques and methods?]

• Different techniques are appropriate for different types of system.

• Games vs Safety critical systems

  • 게임은 더 flexible한 software process (accommodates rapid change)가, Safety critical systems는 V model (A complete specification to be developed)가 적합함

Software products

• Generic products

  • Stand-alone systems that are marketed and sold to any customer who wishes to by them.

  • Examples - PC software such as word processors, drawing packages, and project management tools.

• Customized products

  • Software that is commissioned by a specific customer to meet their own needs.
  • Examples - air traffic control software, traffic monitoring systems, embedded control systems.

Product specification

• Generic products

  • The specification of what the software should do is owned by the software developer and decisions on software change are made by the developer.

• Customized products

  • The specification of what the software should do is owned by the customer for the software and they make decisions on software changes that are required.

• -> The distinction between these product types is becoming increasingly blurred.

Essential attributes of good Software

• Maintainability

  • Software should be written in such a way so that it can evolve to meet the changing needs of customers.
  • This is critical attribute because software change is an inevitable requirement of a changing business environment.

• Dependability(믿을 수 있음) and security

  • Software dependability includes a range of characteristics including reliability, security and safety.
  • Dependable software should not cause physical or economic damage in the event of system failure.
  • Malicious users should not be able to access or damage the system.

• Efficiency

  • Software should not make wasteful use of system resources such as memory and processor cycles.
  • Efficiency therefore includes responsiveness(민감도), processing time, memory utilisation, etc

• Acceptability (수용성)

  • Software must be acceptable to the type of users for which it is designed.

  • This means that is must be understandable, usable and compatible with other systems that they use.

SW engineering ethics

SW engineering ethics

• 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(받치다) the law but involves following a set of principles that are morally correct.

Issues of professional responsibility

• Confidentiality (기밀 유지)

  • Engineers should normally respect the confidentiality of their employers or clients irrespective of whether a formal confidentiality agreement has been signed. (client의 기밀 유지)

• Competence (능력)

  • Engineers should not misrepresent their level of competence.

  • They should not knowingly accept work which is outwith their competence. (엔지니어들은 자기 능력을 outwith 하면 안됨)

• 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.

• 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).

ACM / IEEE Code of Ethics

• Members of these organisations such as ACM, IEEE sign up to the code of practice when they join.

  • ACM: Association for Computing Machinery

  • IEEE: Institute of Electrical and Electronics Engineers

• Software engineers shall adhere to the eight principles.

  1. 공익 (Public): 소프트웨어 엔지니어는 공공 이익과 일관되게 행동해야 합니다. 즉, 사회적 책임을 다하고 대중의 이익을 고려해야 합니다.

  2. 고객 및 고용주 (Client and employer): 소프트웨어 엔지니어는 고객과 고용주의 이익을 고려하여 행동해야 합니다. 이때, 공공 이익을 해치지 않는 범위에서 그들의 이익을 존중해야 합니다.

  3. 제품 (Product): 소프트웨어 엔지니어는 자신의 제품과 관련 수정 사항이 최고의 전문적 표준을 준수하도록 보장해야 합니다.

  4. 판단 (Judgement): 소프트웨어 엔지니어는 전문적인 심사에서 무결성과 독립성을 유지해야 합니다. 다른 이해관계자의 영향을 받지 않고 윤리적 판단을 내려야 합니다.

  5. 관리 (Management): 소프트웨어 엔지니어 관리자와 리더는 소프트웨어 개발과 유지 관리의 윤리적 접근 방식을 지지하고 홍보해야 합니다.

  6. 직업 (Profession): 소프트웨어 엔지니어는 직업의 품위와 평판을 공공 이익과 일관되게 향상시켜야 합니다.

  7. 동료 (Colleagues): 소프트웨어 엔지니어는 동료에게 공정하고 지원적이어야 합니다. 협력과 상호 지원을 촉진해야 합니다.

  8. 자기 (Self): 소프트웨어 엔지니어는 자신의 전문 분야에 대한 평생 학습에 참여해야 하며, 직업 수행에 대한 윤리적 접근 방식을 촉진해야 합니다.

Case Study

• 인슐린 펌프 제어 시스템 (An Insulin Pump Control System): 당뇨병 환자가 혈당을 조절하기 위해 사용하는 인슐린 펌프의 내장 시스템

  • Key roles

    1. Collect information from a blood sugar sensor.
    2. Calculate the amount of insulin required to be injected.
    3. Deliver a controlled dose of insulin to a user.
       

  • Essential high-level requirements

    • The system shall be available to deliver insulin only when required.
    • The system shall perform reliably and deliver the correct amount of insulin to counteract the current level of blood sugar.
    • The system must therefore be designed and implemented to ensure that the system always meets these requirements.

• 정신 건강 환자 관리 시스템 (Mentcare - A Mental Health Case Patient Management System): 정신 건강 문제를 가진 환자의 기록을 유지하고 관리하는 시스템

• 야외 날씨 관측소 (A Wilderness Weather Station): 원격 지역에서 날씨 조건에 관한 데이터를 수집하는 데이터 수집 시스템

• iLenar: 디지털 학습 환경 (a Digital Learning Environment): 학교에서 학습을 지원하기 위한 시스템으로, 디지털 학습 환경을 제공