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1 CS 501 Spring 2003
CS 501: Software Engineering
Lecture 1
Introduction to Software Engineering
2 CS 501 Spring 2003
About the Course
Web site: www.cs.cornell.edu/Courses/cs501/2003sp/
Email: [email protected]
Instructor: William Arms
Teaching assistants: Ken Hopkinson, Natalya Katsnelson
Assistant: Anat Nidar-Levi
Computer lab: Computer Science Undergraduate Lab, Upson Hall, Room 315/317.
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Course Administration
Sign up sheets
Please return at end of class
To contact members of the course team, send email to:
Do not send email to the instructor or an individual TA, except for questions to the TA assigned to your project.
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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, with proper 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.
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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
Five quizzes held during class times. No examinations. (See Syllabus on the Web site for details.)
Wednesday evening
One or two lectures will be given on Wednesday evenings. Otherwise this time is available for project meetings.
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About the Course
Readings:
Required readings. Material that will be tested in the quizzes
Background reading. Recommended material, that will not be tested explicitly
Textbook
There is no course textbook. In the past the two following books have been used.
Sommerville, Ian, Software Engineering, Fifth Edition. Addison-Wesley, 1996.
Pfleeger, Shari Lawrence, Software Engineering Theory and Practice, second edition. Prentice- Hall 2001.
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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 15
• Group presentations and reports:
requirements, design, final
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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
• Advertise at the beginning of class
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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
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Grading (Subject to Change)
Project (group) 45%
Project (individual) 25%
Quizzes 30%
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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.
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Variety of Software Products
Examples
Real time: air traffic control Embedded systems: digital camera, GPSData processing: telephone billing, pensionsInformation systems: web sites, digital librariesSensors: weather dataSystem software: operating systems, compilersCommunications: routers, mobile telephonesOffices: word processing, video
conferencesScientific: simulations, weather forecastingGraphical: film making, design etc., etc., etc., ....
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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?
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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
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Observations about Big Projects
• A CS501 project is about 0.3 person/years. A big project is 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.
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Previous Experience (Mine)
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.)
Much of my career, I was in charge of computing at Dartmouth and Carnegie Mellon, with some time in industry.
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Future Experience
What will you be doing one year from now?
Ten years from now?
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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 itetc.
Failures of software development projects can bankrupt companies!
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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 timeetc.
The people who take the responsibility must know what is happening!
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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!
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Course Themes: Scale
Techniques for large and very large systems
• Software design
Software architecture Object-oriented design
• Dependable systems
Reliability Verification
• Legacy systems
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Software as a Product
Software is expensive!
The major cost is your salary!
Every software project has a trade-off between:
Functionality Resources (cost) Timeliness
Example: Andrew console monitor
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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: DEC's optical scanner
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What is Good Software?
Client (a.k.a. Customer)
The client provides resources and expects some product in return.
Client satisfaction is the primary measurement of success.
Question: Who is the client for Microsoft Excel?
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Categories of Product
Categories of client and software product:
• Generic (e.g., Microsoft Excel)
• Bespoke (customized) (e.g., IRS internal system)
Many systems are customized versions of generic packages (e.g., Cornell's payroll system)
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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 craft of software engineering is to select appropriate methods for each project and apply them effectively.
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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).
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Next Steps
• Selection of projects -- read the Web site.
• Form project teams.
