CS 501: Software Engineering

1. CS 501: Software Engineering Lecture 1 Introduction to Software Engineering

2. New CIS Course CIS 435/635: Seminar on Applications of Information Science Instructor: Paul Ginsparg This seminar course examines the technological, sociological, legal, financial and political aspects of information systems in the context of innovative applications. The course is designed as a series of case studies in information science. Examples will include arXiv, NSDL, NuPrl, the Legal Information Institute, Protomap, Dspace, and others created or maintained within Cornell, as well as some representative exterior resources. Time and place: Tuesday and Thursday 11:40-12:55pm, Information Science seminar room, 301 College Avenue.

3. About the Course Web site: www.cs.cornell.edu/Courses/cs501/2004sp/ Email: cs501-l@cs.cornell.edu (student to course team) Newsgroup: cornell.class.cs501 (student to student) Instructor: William Arms Teaching assistants: Ken Hopkinson, Aseem Bajaj Assistant: Anat Nidar-Levi Computer lab: Computer Science Undergraduate Lab, Upson Hall, Room 315/317.

4. Course Administration Sign up sheets Please return at end of class Email To contact members of the course team, send email to: cs501-l@cs.cornell.edu Do not send email to the instructor or an individual teaching assistant, except for questions to the teaching assistant assigned to your project.

5. Academic Integrity Software Engineering is a collaborative activity. You are encouraged to work together, but ... Some tasks may require individual work. Always give credit to your sources and collaborators. Good professional practice: To make use of the expertise of others and to build on previous work, withproper attribution. Unethical and academic plagiarism: To use the efforts of others without attribution. See: Code of Academic Integrity on the course Web site, which points to the Cornell code.

6. About the Course Syllabus For the schedule of lectures, assignments, readings and quizzes, see the Syllabus file on the course Web site. (Note that this syllabus will change as the course progresses.) Quizzes Four quizzes held during class times. No examinations. (See Quizzes on the Web site for details.) Wednesday evening One or two classes may be given on Wednesday evenings. Otherwise this time is available for project meetings.

7. About the Course Readings: Required readings. Material that will be tested in the quizzes will be identified during classes. Background reading. Recommended material, that will not be tested explicitly. Textbook: There is no course textbook.  See the Web site for general books on Software Engineering. See the Books and Readings file on the Web site.

8. Grading (Subject to Change) Project (group) 45% Project (individual) 25% Quizzes 30%

9. Overall Aim of the Course We assume that you are technically proficient. You know a good deal about computing, can program reasonably, can learn more on the job. When you leave Cornell, you are going to work on production projects where success or failure costs millions of dollars. Soon you will be in charge! It may be your money! We want you to make your mistakes now and learn from your mistakes.

10. Projects The Course is Built around the Projects • Real project for real client who intends to use the software in production. • Select your own project, any branch of software engineering •Project teams, about 5 to 7 people. • Feasibility study and plan: due February 20 • Group presentations and reports: requirements, design, final The class on Thursday will discuss the projects.

11. Project Selection Read the Web site •Some projects are suggested on the Web site and will be discussed in class on Thursday • You are encouraged to find other projects Contact potential clients • Gain idea of their expectations • Estimate scope and complexity of the project • Discuss business decisions Assemble project team • Post message on newsgroup cornell.class.cs501 • Advertise at the beginning of class

12. Thoughts about Project Selection Projects • Target must be a production system (not research) • Client should be one or two designated people -- client should be prepared to meet with you regularly and attend the presentations Team • Teams need many strengths -- organizational, technical, writing, etc. • Consider appointing a leader to coordinate the effort

13. Variety of Software Products Examples Real time: air traffic control Embedded systems: digital camera, GPS Data processing: telephone billing, pensions Information systems: web sites, digital libraries Sensors: weather data System software: operating systems, compilers Communications: routers, mobile telephones Offices: word processing, video conferences Scientific: simulations, weather forecasting Graphical: film making, design etc., etc., etc., ....

14. Client Client (a.k.a. Customer) The client provides resources and expects some product in return. Client satisfaction is the primary measurement of success in a software project. Question: Who is the client for Microsoft Excel?

15. Categories of Software Product Categories of client and software product: • Generic (e.g., Microsoft Excel) • Packages (e.g., Mathematica) • Customized versions of generic packages (e.g., Cornell's payroll system) • Bespoke (customized) (e.g., IRS internal system) • Demonstration, prototype, research, ... Who is the client for each category of product?

16. Previous Experience (Yours) Your background • Biggest program that you have written? • Biggest program that you have worked on? • Biggest project team that you have been part of? • Longest project that you have worked on? • Most people who have used your work? • Longest that your project has been in production?

17. Observations Most software development is by teams • Effectiveness of team determines success Most large software projects are built on older ones • It is rare to start a new suite of programs from scratch • Building on the work of others is a fundamental skill of software development

18. Observations about Big Projects • A CS501 project is about 0.3 person/years. A big project may be 100 to 1,000+ person years. • Every important program is written by many people, who are constantly changing. • Before a big project is completed the requirements have changed many times. • No large system is ever complete.

19. Future Experience What will you be doing one year from now? Ten years from now? Typical career paths in computing combine technical work with varying degrees of project management, marketing, entrepreneurship, etc.

20. Previous Experience (Mine) Much of my career, I was in charge of computing at Dartmouth and Carnegie Mellon, with some time in industry. Projects where I was in charge • Operating system, compilers, etc. • Two campus networks, routers, SNMP, etc. • Distributed computing environment, file systems, etc. • Administrative data processing, general ledger, etc. • Digital libraries (including current large project for the National Science Foundation) (Theme has been first production system where the methods have previously been used only in research.)

21. Software is Expensive Software is expensive! The major costs are salaries (your salaries)! Every software project has a trade-off between: Functionality Resources (cost) Timeliness Example: Console monitor

22. Course Themes: Risk Risk (as Seen by a Manager) •Problems Over budget Late delivery Does not work as expected •Never used Does the wrong thing Needs change Users dislike to use it etc. Failures of software development projects can bankrupt companies!

23. Course Themes: Visibility Visibility (as Seen by a Manager) •Problem Must rely on others for reports of progress or difficulties •Software Developers Have difficulty evaluating progress Optimistic Consider reporting a waste time etc. The people who take the responsibility must know what is happening!

24. Course Themes: Process Process in Large Software Projects • Software as a product Clients and their needs Quality • Requirements and specification Usability Evolution • Project management Personnel management Economic, legal, and social factors Nobody comprehends more than a fraction of the project!

25. Course Themes: Scale Techniques for large and very large systems • Software design Software architecture Object-oriented design • Dependable systems Reliability Verification • Legacy systems

26. What is Good Software? General characteristics Usability Maintainability Dependability Efficiency Good software products require good programming, but ... Programming quality is the means to the end, not the end itself. Example: Optical scanner

27. The Craft of Software Development Software products are very varied --> Client requirements are very different --> There is no standard process for software engineering --> There is no best language, operating system, platform, database system, development environment, etc. A skilled software developer knows about a wide variety of approaches, methods, tools. The craftof software engineering is to select appropriate methods for each project and apply them effectively.

28. Professional Responsibility • Organizations put trust in software developers: • Competence: Software that does not work effectively can destroy an organization. • Confidentiality: Software developers and systems administrators may have access to highly confidential information (e.g., trade secrets, personal data). • Legal environment: Software exists in a complex legal environment (e.g., intellectual property, obscenity). • Acceptable use and misuse: Computer abuse can paralyze an organization (e.g., the Internet worm).

29. Next Steps • Read the Web site. • Begin planning for your projects and forming project teams.