COMS W4156: Advanced
Software Engineering
Prof. Gail Kaiser
Kaiser+4156@cs.columbia.edu
http://bank.cs.columbia.edu/classes/cs4156/
September 8, 2009
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Objectives of this course
• To introduce advanced concepts in software
engineering and their embodiment in selected
methodologies and technologies
• To apply those concepts within a multi-iteration
team software development project
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Topics covered in this lecture
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Overview of software engineering
Overview of the course
Pair design exercise
If time permits: Introduction to pair programming
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Software Engineering as a Discipline
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What is software?
• Computer programs and associated documentation
such as requirements, design models, test plans and
user manuals.
• Software products may be developed for a particular
customer or may be developed for a general market.
• New software can be created by developing new
programs, customizing generic software systems
and/or combining existing software.
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What is software engineering?
• Software engineering is an engineering discipline that is
concerned with all aspects of software production.
– NOT just programming
– NOT just programming [part of] a large software system
– NOT just programming as a member of a large team
• Software engineering is a systematic and organized approach
to software development using appropriate tools and
techniques depending on the problem to be solved, the
development constraints and the resources available.
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What do software engineers do?
• Anyone can call themselves a software engineer, but
not all programmers are software engineers (and not
all software engineers are programmers)
• Newly hired software engineers typically assigned to
test or maintain someone else’s pre-existing code
• Maintenance = Everything after initial deployment
– When was the last time you used a commercial or open
source program labeled “Version 1.0”?
– 50-90+% of total lifecycle costs
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What do software engineers do?
• Categories of maintenance
– Corrective - reactive modification to correct discovered
problems
– Adaptive - modification to keep it usable in a changed or
changing environment
– Perfective - improve performance or maintainability
– Preventive - modification to detect and correct latent
faults
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What is the difference between software
engineering and computer science?
• Computer science is concerned with theory and
fundamentals.
• Software engineering is concerned with the
practicalities of developing and delivering useful
software.
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Why study software engineering?
• Writing a program is easy
– Program ~= code (possibly with comments)
• Developing a software system is harder
– System ~= program plus technical documentation sufficient such
that someone other than original developers can maintain and
extend
• Developing a software product is very hard
– Product ~= system plus customers, fulfilling the business needs of
those customers, with customer-oriented documentation and
support
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Why study software engineering?
• To attain high-quality software products, software engineers
must be skilled professionals who follow defined processes
and “best practices”
• Some schools offer entire degree programs in software
engineering (e.g., CMU, Drexel)
• At present there is no licensing of software engineers in the
US, only specialty “certifications” offered by vendors (e.g.,
IBM, Microsoft, Sun) and by vendor-neutral organizations
(e.g., IEEE, Linux Professional Institute)
• Most other kinds of “engineer” must be licensed by the state
government, but licensing of software engineers is very
controversial
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THIS Software Engineering course
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Course content
•
Software process
–
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Component-based software development
–
•
Pair programming, requirements, modeling,
architecture, design patterns, refactoring, …
Component model frameworks (COM+, .NET, EJB,
Web Services)
Quality assurance
–
Code inspection, unit and integration testing, stress
testing, test planning
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Why is this course called Advanced
Software Engineering?
• Until ~2002, undergraduate CS majors were required to take COMS
W3156 Introduction to Software Engineering, oriented towards
sophomores and juniors, whereas 4156 was an equivalent elective
oriented towards seniors and graduate students
• Both courses presented a traditional view of the software lifecycle
focused on detailed documentation, independent of any particular
implementation technology, and stepped through the full lifecycle
(through delivery to “customers”)
• 3156 replaced by COMS W3157 Advanced Programming
• 4156 now assumes introductory level software engineering background
(preferably from the real world)
• Concentrates on recent trends towards component technology and
emphasizes quality assurance
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Who am I?
•
•
•
•
•
Gail Kaiser
kaiser+4156@cs.columbia.edu (note the +4156)
Professor at Columbia since 1985
BS from MIT, MS and PhD from CMU
Worked summers and/or consulted for startups, defense
contractors, industry research labs, Software Engineering
Institute, Educational Testing Service
• Research in software testing, collaborative work, computer
and network security, parallel and distributed systems, selfmanaging systems, Web technologies, information
management, software development environments and tools
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Who are the TAs?
• Mr. Nipun Arora, third year graduate student
• Mr. Palak Baid, second year graduate student
• Mr. Jonathan Bell, senior in SEAS
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Who are you?
• Graduate and upper level undergraduate students in
Computer Science, Computer Engineering, Biomedical
Informatics, Electrical Engineering, IEOR, maybe others
• Sincerely interested (hopefully) in learning to apply Software
Engineering methodologies and technologies – not just
programming skills – to developing useful and usable
software products
• 4156 is required for the CS MS Software Systems track (unless
you “import” a prior upper-level software engineering
course from another institution)
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Textbooks
• Required: Ian Sommerville, Software Engineering, 8th
edition, Addison-Wesley, ISBN 9780321313799
• Recommended: Ron Patton, Software Testing, 2nd
edition, Sams Publishing, ISBN 0672327988
• Ordered for this class through the Columbia
University Bookstore
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Final Grade Breakdown
• 50% Team Project
– 2 iterations @ 25% each
• 40% Individual Assessments [exams]
– 20% midterm
– 20% final
• 10% Class participation and “pop quizzes”
• Assignments must be submitted via CourseWorks
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Team Project
• Students work primarily in pairs (2 people)
• Grouped into 2-pair teams (4 people)
• Each team will invent, design, code and test a very
small software system using some component model
framework
• 2 rapid iterations of project - each ~3 weeks long
• All major system functionality should be (more or
less) operational by the end of the 1st iteration
• 2nd iteration will focus on quality assurance issues
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Pairs and Teams
• Pairs ideally self-chosen – find a partner (if odd enrollment,
one triplet permitted but no onesies)
• Meet someone in class or advertise on the 4156 discussion
forum on CourseWorks
• 2 pairs can request each other for a team
• Unattached individuals and pairs will be assigned by the
teaching staff
• Each team will submit a proposal for the very small system
they want to develop
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Do the Team Project AS A TEAM
1. Develop and test your project code together
with your pair partner
2. Integrate together with your team’s other pair
3. Co-author project documentation with all team
members
4. Demonstrate your project to the teaching staff
 All members of the same team must use
the same component model framework
(e.g., EJB, .NET)
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Project Grading
• Team members who do not contribute appropriately should
be brought to the attention of the teaching staff as soon as
possible.
• Such team members may receive a significantly lower grade
for the relevant project assignment(s) than the rest of that
team, possibly "zero", may be reassigned to another team,
and/or may be asked to withdraw from the course.
• Team members who contribute “above and beyond the call
of duty” may receive a higher grade than the rest of the
team
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Frequently Asked Questions
• Do I have to join a pair/team?
YES!
• Can I do the project alone?
NO!
• I work full time, I have a heavy class schedule, I have a long commute,
I don’t like working in groups, I prefer to program in an obscure
language that no one else knows, etc. - Can I do the project alone?
NO!
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Frequently Asked Questions
• Do we have to use a component model framework?
YES!
• Can we use a component model framework not covered in class?
Yes, but only if it provides
component services for developing
N-tier applications
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Individual Assessments
• Midterm and Final
• Take-home examinations that must be completed by
each student working individually
• Demonstrate your understanding of software
engineering principles and technologies, and how
they are applied (graded)
• Evaluate your own, your partner’s and your team’s
work on the project thus far (not graded, but
contributes to project grade differentials)
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Class Participation
• Attendance is required
• Short “pop quizzes” will be given during several
class periods
• Please ask questions of general interest in class
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Final Grade Breakdown
• 50% Team Project
– 2 iterations @ 25% each
• 40% Individual Assessments [exams]
– 20% midterm
– 20% final
• 10% Class participation and “pop quizzes”
• Assignments must be submitted via CourseWorks
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Pair Design Exercise
(details announced in class)
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Pair Programming
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What Is Pair Programming?
• Two software engineers work side-by-side at one
computer, sliding keyboard and mouse back and
forth (or simulated via desktop sharing technologies)
• Continuously collaborate on same design, algorithm,
code, test, etc.
• Continuous informal review
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What Is NOT Pair Programming?
• Splitting up the work
• Taking turns doing the work
• One person doing all the work
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What About Productivity?
• Very controversial – common practice in some software
development organizations and unthinkable in others
• Demonstrated in some studies to improve productivity
and quality of software products under some
circumstances
– Particularly novice-novice pairs (vs. novice solos) or expertexpert pairs (vs. expert solos)
– Two programmers work together nearly twice as fast and think
of more solutions to a problem as two working alone
– While attaining higher defect prevention and defect removal
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Benefits
• Increased discipline. Pairing partners are more
likely to "do the right thing" and are less likely to
take long breaks.
• Fewer interruptions. People are more reluctant to
interrupt a pair than they are to interrupt someone
working alone.
• Resilient flow. Pairing leads to a different kind of
mental dynamic than programming alone.
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Benefits
• Better code. Pairing partners are less likely to produce a bad
design due to their immersion, and tend to come up with
higher quality designs.
• Multiple developers contributing to design. If pairs are
rotated frequently, several people will be involved in
developing a particular feature. This can help create better
solutions, particularly when a pair gets stuck on a particularly
tricky problem
• Collective code ownership. When everyone on a project is
pair programming, and pairs rotate frequently, everybody
gains a working knowledge of the entire codebase.
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Benefits
• Mentoring. Everyone, even junior programmers,
possess knowledge that others don't. Pair
programming is a way of spreading that knowledge.
• Improved morale. Pair programming can be more
enjoyable for some engineers than programming
alone.
• Team cohesion. People get to know each other
more quickly when pair programming. Pair
programming may encourage team gelling.
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Drawbacks
• Experienced developers may find it tedious to tutor a less
experienced developer in a paired environment.
• A less experienced developer may feel intimidated pairing
with a more experienced developer, which may result in less
participation.
• Differences in coding style may result in conflict.
• Personality conflicts can result in one or both developers
feeling awkward or uncomfortable.
• Some software engineers prefer to work alone, and may find
the paired environment cumbersome.
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Drawbacks
• In the case where the team has slightly different work
schedules, which is common in an environment that values
work-life balance, the pair is only available during the overlap
of their schedules. Therefore, not only does it require more
man-hours to complete a task, a typical day has fewer pairhours available, which further increases the overall task
completion time.
• Where a company values telecommuting (working from
home) or when an employee must work from outside the
office for whatever reasons, pair programming can be
difficult.
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Final Notes
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First Assignment Due Next Week!
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•
•
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Due Tuesday 15 September, 10am
Posted on course website
Submit via CourseWorks
Pair Formation
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Upcoming Deadlines
• Teams announced September 22nd
• Team project concept due September 29th
• Project concept feedback by October 6th
First iteration begins October 6th
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COMS W4156: Advanced
Software Engineering
Prof. Gail Kaiser
Kaiser+4156@cs.columbia.edu
http://bank.cs.columbia.edu/classes/cs4156/
September 8, 2009
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