The Definition of “ Software Engineering ”

1. The Definition of “Software Engineering” A discipline that requires the knowledge of mathematical and natural sciences gained by study, experience and practice is applied to the systematic development of correct, consistent and maintainable software products. Lecture 1

2. The Nature of Software • Software is intangible • Software is easy to reproduce • Cost is in its development • in other engineering products, manufacturing is the costly stage • The industry is labor-intensive • Hard to automate Lecture 1

3. The Nature of Software • Much software has poor design and is getting worse • Demand for software is high and rising • We are in a perpetual ‘software crisis’ • We have to learn to ‘engineer’ software Lecture 1

4. What is Software Engineering? • The process of solving customers’ problems by the systematic development and evolution of large, high-quality software systems within cost, time and other constraints • Other definitions: • IEEE: (1) the application of a systematic, disciplined, quantifiable approach to the development, operation, maintenance of software; that is, the application of engineering to software. (2) The study of approaches as in (1). Lecture 1

5. What is Software Engineering? • Solving customers’ problems • This is the goal of software engineering • Sometimes the solution is to buy, not build • Adding unnecessary features does not help solve the problem • Software engineers must communicate effectively to identify and understand the problem Lecture 1

6. What is Software Engineering? • Systematic development and evolution • An engineering process involves applying well understood techniques in a organized and disciplined way • Many well-accepted practices have been formally standardized • e.g. by the IEEE or ISO • Most development work is evolution Lecture 1

7. What is Software Engineering? • Large, high quality software systems • Software engineering techniques are needed because large systems cannot be completely understood by one person • Teamwork and co-ordination are required • Key challenge: Dividing up the work and ensuring that the parts of the system work properly together • The end-product must be of sufficient quality Lecture 1

8. What is Software Engineering? • Cost, time and other constraints • Finite resources • The benefit must outweigh the cost • Others are competing to do the job cheaper and faster • Inaccurate estimates of cost and time have caused many project failures Lecture 1

9. Software Engineering • Software engineering as a discipline is focused on • To significantly increase software productivity (P) and software quality (Q) while reducing software costs (C) and time to market (T) – software PQCT Lecture 1

10. Types of Software • Custom • For a specific customer • Generic • Sold on open market • Often called • COTS (Commercial Off The Shelf) • Shrink-wrapped • Embedded • Built into hardware • Hard to change Lecture 1

11. Types of Software • Real time software • Example: control and monitoring systems • Must react immediately • Safety often a concern • Data processing software • Used to run businesses • Accuracy and security of data are key • Some software has both aspects Lecture 1

12. Challenges posed by Software • How do we ensure “quality”? • How do we define “quality”? • How do we measure “quality”? • Will a quality defined for one software product be applied to another software product? • We can do that for hardware products if one product is a component of another • Does the definition of a particular quality remain the same forever? Lecture 1

13. Challenges posed by Software (continued) • How do we cope with “aging” software? • often encounter the situation that a software product becomes old and needs replacement • The rate of “aging” does not seem to be predictable • a payroll application written in COBOL used in IBM mainframe for 17 years, but the next payroll application written in Pascal/C running on DEC VMS last for only 8 years Lecture 1

14. Challenges posed by Software (continued) • How often we need to upgrade software? • Windows 95 was replaced by Windows 98 and was then replaced by Windows Millennium, Windows XP, now Windows Vista, Windows 7 • Will the application programs/data written in the previous version still be usable in the next version? • What are the chances of failures? • What about the cost of upgrades? Lecture 1

15. Challenges posed by Software (continued) • How to develop software on or before the deadline? • until 1999, more than 80% of software projects were finished only AFTER the deadline • in many cases, software development projects went beyond the deadline limits that the customers cancelled the projects • what need to be done to meet the deadline? Lecture 1

16. Goals of Software Engineering Education • To develop correct, consistent and maintainable software products • To meet deadlines while developing software products • To make software development processes well-documented and easily accessible so that newcomers to a software development project can join and continue without much difficulties (must reduce training overhead) • To make software development processes visible to a hierarchy of people involved in the development process • … Lecture 1

17. Software Engineering and the Engineering Profession • The term Software Engineering was coined in 1968 • People began to realize that the principles of engineering should be applied to software development • Engineering is a licensed profession • In order to protect the public • Engineers design artifacts following well accepted practices which involve the application of science, mathematics and economics • Ethical practice is also a key tenet of the profession • In many countries, much software engineering does not require an engineering license, but is still engineering Lecture 1

18. Computer Science Pursue optimal solutions $$$ is not an important consideration Programming in the small Technical issues Dealing with tame problems Foundations of software engineering Software Engineering Good enough is enough $$$ is an important factor (PQCT) Programming in the large All issues and aspects Dealing with wicked problems Building on top of computer science and other disciplines Software Engineering and Computer Science

19. Software Engineering and the Engineering Profession Ethics in Software Engineering: Software engineers shall • Act consistently with public interest • Act in the best interests of their clients • Develop and maintain with the highest standards possible • Maintain integrity and independence • Promote an ethical approach in management • Advance the integrity and reputation of the profession • Be fair and supportive to colleagues • Participate in lifelong learning Lecture 1

20. Stakeholders in Software Engineering • Users • Those who use the software • Customers • Those who pay for the software • Software developers • Development Managers All four roles can be fulfilled by the same person Lecture 1

21. Software Quality • Usability • Users can learn it and fast and get their job done easily • Efficiency • It doesn’t waste resources such as CPU time and memory • Reliability • It does what it is required to do without failing • Maintainability • It can be easily changed • Reusability • Its parts can be used in other projects, so reprogramming is not needed Lecture 1

22. Customer: User: solves problems at easy to learn; an acceptable cost in efficient to use; terms of money paid and helps get work done resources used QUALITY SOFTWARE Development manager: Developer: sells more and easy to design; pleases customers easy to maintain; while costing less easy to reuse its parts to develop and maintain Software Quality and the Stakeholders Lecture 1

23. Software Quality: Conflicts and Objectives • The different qualities can conflict • Increasing efficiency can reduce maintainability or reusability • Increasing usability can reduce efficiency • Setting objectives for quality is a key engineering activity • You then design to meet the objectives • Avoids ‘over-engineering’ which wastes money • Optimizing is also sometimes necessary • Example: obtain the highest possible reliability using a fixed budget Lecture 1

24. The 4P Model Software Engineering involves … Product Process Process People Product People Project Project Lecture 1

25. Software Engineering Projects • Most projects are evolutionary or maintenance projects, involving work on legacy systems • Corrective projects: fixing defects • Adaptive projects: changing the system in response to changes in • Operating system • Database • Rules and regulations • Enhancement projects: adding new features for users • Reengineering or perfective projects: changing the system internally so it is more maintainable Lecture 1

26. Software Engineering Projects • ‘Green field’ projects • New development • The minority of projects Lecture 1

27. Software Engineering Projects • Projects that involve building on a framework or a set of existing components • A framework is an application that is missing some important details • Example: Specific rules of this organization • Such projects: • Involve plugging together components that are: • Already developed. • Provide significant functionality • Benefit from reusing reliable software • Provide much of the same freedom to innovate found in green field development Lecture 1

28. Activities Common to Software Projects • Requirements and specification • Domain analysis • Defining the problem • Requirements gathering • Obtaining input from as many sources as possible • Requirements analysis • Organizing the information • Requirements specification • Writing detailed instructions about how the software should behave Lecture 1

29. Activities Common to Software Projects • Design • Deciding how the requirements should be implemented, using the available technology • Systems engineering: Deciding what should be in hardware and what in software • Software architecture: Dividing the system into subsystems and deciding how the subsystems will interact • Detailed design of the internals of a subsystem • User interface design • Design of databases Lecture 1

30. Activities Common to Software Projects • Modeling • Creating representations of the domain or the software • Use case modeling • Structural modeling • Dynamic and behavioral modeling • Implementation • Quality Assurance • Reviews and inspections • Testing • Maintenance Lecture 1

31. A Software Engineering Process Identify Corporate practices Plan Configuration Management Plan Quality Assurance Plan verification and validation methods Plan development process Analyze Requirements Design Implement Test Maintain Lecture 1

32. Software Engineering Process Lecture 1

33. Standards and Practices Provide a disciplined approach to software development process Standards IEEE, ISO, ANSI, … Practices CMM, Rational, … Lecture 1

34. Capability Maturity Model (CMM) • Developed by Software Engineering Institute (SEI) at Carnegie-Mellon in 1980s • Department of Defense wanted to establish the standards for software development organizations in order to restrict bidding for government contracts • Result: organizations have to be certified as CMM-Level (?) for bidding government contracts Lecture 1

35. CMM Lecture 1

36. CMM • Level 1: Initial • ad hoc processes; no formalized method for any activity • no project plans • success depends on efforts of individuals in the organization • software development process continuously changes Lecture 1

37. CMM • Level 2: Repeatable • basic project management established • project plan incorporated; estimates are realistic and based on previous projects • purpose: to track cost, schedule and functionalities • process improvement occurs based on the success of previous projects (that is why the level is called “repeatable”) Lecture 1

38. CMM • Level 3: Defined • processes are documented, standardized and integrated with other processes • project management refined from previous level • every process (activity) is verified; subject to the standards established; modifications and new processes are documented • in short, an iterated version of level 2 Lecture 1

39. CMM • Level 4: Managed • both process management and product management incorporated • quantitative analysis of processes and products conducted; measurement procedures for quantitative analysis are established • in short, “quality assurance of products” is given more importance at this level Lecture 1

40. CMM • Level 5: Optimizing • introduces research-oriented processes to continuously improve (to optimize) the existing processes and policies • best software engineering processes and management practices are used throughout the organization Lecture 1

41. Exercise • Software Engineering Institute (SEI) at Carnegie Mellon University developed Capability Mature Model Integration (CMMI) in 2007. Find out the differences between CMM and CMMI. Lecture 1