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ECE 417/617: Elements of Software Engineering

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Title: ECE 417/617: Elements of Software Engineering


1
Introduction
ECE 417/617 Elements of Software Engineering
Stan Birchfield Clemson University
2
Why does this course exist?
  • Software is becoming more and more
  • important
  • complex
  • Software is everywhere, at multiple levels
    System, application, scientific, embedded,
    ubiquitous, web, AI,
  • We still do not know how to do it
  • Techniques that we have been using for 60 years
    are inadequate
  • Software engineering is an attempt to solve this
    problem
  • Expect several generations for new
    habits/principles/procedures to be
  • discovered
  • transmitted (education)
  • Adopted (replacing old habits)

3
The Software Crisis
  • Standish Group (1995) studied S/W projects
  • 16 successful (fully functional, on-time, and
    on-budget)
  • 53 challenged (reduced functionality, late,
    over-budget)
  • 31 failed (cancelled)
  • More recent data (2006) suggests an improvement
    35, 46, and 19

4
Famous Bugs
  • 1997 Mars Pathfinder
  • three tasks low-priority (weather data),
    medium-priority (communications), high-priority
    (information bus)
  • priority inversion Med interrupted Low before
    High could execute
  • watchdog timer repeatedly rebooted system because
    High had not executed in time
  • on-board debugging fixed the problem
  • http//www.ece.cmu.edu/raj/mars.html
  • 1999 Mars Climate Orbiter
  • Smashed into planet because units were not
    converted from English to metric
  • 125 million spacecraft lost
  • 2004 Mars rover Spirit
  • Just after launch (June 2003), bug found in S/W,
    new version uploaded
  • This caused side-effect, so another version
    uploaded
  • After a few days, rover went into infinite reboot
  • Longest trial for file system testing was 9 days
  • 2004 Air traffic controller in Southern
    California
  • Microsoft server timed to shut down automatically
    every 49.7 days to prevent data overload (232
    milliseconds)
  • Technicians normally reboot system every 30 days
    to avoid this
  • One technician forgot ? system shut down on its
    own
  • 800 planes were left in the air without contact
    5 near misses

5
Another glitch
  • "Last year in South Africa an anti-aircraft had a
    'software glitch' during a training exercise," he
    says. "It was supposed to fire upwards into the
    sky, instead it lowered and it fired in a circle
    and killed nine soldiers, all because of a
    software glitch."
  • http//www.cnn.com/2009/WORLD/americas/07/23/wus.w
    arfare.remote.uav/index.html

6
S/W in automobiles
  • Average automobile has
  • 70 to 100 microprocessor-based electronic control
    units (ECUs), running
  • 100 million lines of software code
  • Control software logic analyzes vehicle load,
    engine operations, battery parameters,
    temperatures, ...
  • Software development is the single most important
    consideration in new product development
    engineering
  • 35-40 of the cost of a car is software and
    electronics (13-15 of that cost is software
    development)
  • 50 of car warranty costs are related to
    electronics and embedded software
  • Bugs
  • 2005 Toyota recalled gt160000 Prius hybrids due
    to S/W problem
  • May 2008 Chrysler recalled gt20000 Jeep
    Commanders b/c bug in automatic transmission S/W
  • June 2008 Volkswagen recalled 4000 Passats and
    Tiguans for bug in engine-control-module S/W
  • November 2008 GM recalled gt12000 Cadillacs that
    toggled air bag enable/disable bit

from Robert N. Charette, This Car Runs on Code,
IEEE Spectrum, Feb. 2009
7
What is Software Engineering?
  • The IEEE Computer Society defines software
    engineering as
  • (1) The application of a systematic, disciplined,
    quantifiable approach to the development,
    operation, and maintenance of software that is,
    the application of engineering to software.
  • (2) The study of approaches as in (1)
  • If you do not find this helpful, you are not
    alone
  • A better definition S/W engineering is
    applying sound engineering principles to develop
    reliable, efficient, economic S/W Pressman

8
What is S/W engineering?
  • S/W engineering is about managing complexity and
    change
  • complexity many different conflicting
    objectives, lack of modularity
  • change requirements updated when
    developers/clients get better understanding of
    application, staff turn-around is high, time b/w
    technological changes shorter than duration of
    project The only constant is change
  • S/W engineering
  • focuses on quality (foundation)
  • involves
  • Process defines framework in which S/W is
    developed and managed
  • Methods activities involved
  • Tools support the work

9
What is S/W engineering?
  • Modeling one of the basic methods of science
  • Problem solving lack of fundamental theory
    leads to empirical methods to find solutions
  • Knowledge acquisition knowledge acquisition is
    a non-linear process addition of new piece of
    knowledge may invalidate all previous knowledge
    all activities are interrelated
  • Rationale-driven assumptions change
    continually must capture context in which each
    decision was made

10
Product and process
  • Product end result
  • Process how to get there
  • Often seen as dichotomy (either-or). Field has
    vascillated back and forth over the years between
    the two.
  • In truth, there is a duality. Both are true,
    both are important, need to keep them in balance
    Margaret Davis

11
Balance, balance, balance!
  • If you learn nothing else, remember this
    Balance
  • Lone-ranger mentality has a tendency to reject
    discipline (distrust theory)
  • Academia has a tendency to over-emphasize
    discipline (theory more important than practice)
  • Common sense usually works
  • Be wary of absolutes (in software)
  • Even very good programmers can be trapped by
    adherence to rules rather than focusing on the
    end product

12
The Controversy
  • The term S/W engineering originated in 1968 at a
    conference in Germany
  • But is the term meaningful?
  • S/W is fundamentally different from traditional
    engineering disciplines
  • Not bound by laws of physics
  • Nearly anything can change (plans, people,
    funding, milestones requirements, designs, tests)
  • Metrics have no atomic units and are highly
    subjective
  • Software development is more akin to movie
    production
  • Produces complex web of intellectual property
  • Limited only by vision and creativity
  • It is a blend of science and art
  • Some prefer software development, or software
    economics

Walter Royce, Successful Software Management
Style  Steering and Balance, IEEE Software,
20(5)40-47, 2005
13
Other differences
  • Unlike traditional engineering,
  • S/W is developed, not manufactured
  • Most S/W is still custom-built, not
    component-based construction
  • S/W does not wear out, but it does deteriorate
  • H/W failure curve vs. S/W failure curve
  • S/W projects cannot be managed as if they were
    manufacturing projects

14
S/W Engineering is Management
  • S/W Engineering is about instilling discipline
    into the development process
  • Will make you a better programmer
    (self-management)
  • Is necessary for managing teams of programmers
    (especially large teams)
  • S/W Engineering is a collection of
  • management techniques
  • wisdom and advice gained from past projects
    (successes and failures)
  • abstractions to mediate between low-level code
    and high-level human language

15
What, A Management Course?
  • No, you will not be able to manage a large S/W
    project with hundreds of people by the end of
    this course
  • Management skills take years to develop
  • But, if we are successful, you will
  • Be better able to manage your own code
    development
  • Be equipped to work in (and perhaps lead) a small
    team of programmers
  • Be alert to the struggles and issues faced by
    software managers

16
The Purpose of this Course
  • Encounter the concepts / terms / methods of S/W
    Engineering
  • Some of these are useful
  • Even those that are not You should be familiar
    with them, because you will encounter them
  • Almost all are subject to change / disagreements
  • Understanding the historical context and key
    players is important
  • Gain practical experience
  • Only way to master a craft is to do it
    Learning by doing
  • (Imagine a painting class without paint)
  • Apply concepts as needed
  • Non-linear learning (just in time learning)
    Many concepts will not be taught until after you
    need them
  • Develop proficiency with some additional tools
  • C, VC, CVS,
  • Learn to learn
  • Field is constantly changing
  • Habit and ability to continue learning is
    essential to success

17
Course Mechanics
  • Entire class will work on one project. Class
    will be divided into groups
  • groups will be self-directed, defining own
    milestones and tracking progress
  • Weekly progress updates and goals (in class)
  • Each group will present progress, issues
  • Other groups will offer suggestions
  • Code will be inspected, reviewed
  • Individually,
  • Attendance expected
  • Individual project provides chance to develop
    individual programming skills
  • Weekly written assignments
  • Final exam will cover primarily textbook
    knowledge

18
Certification
  • IEEE Computer Society offers two levels of
    software certification
  • CSDA Certified Software Development Associate
    (introduced in 2008 for those at an entry
    level) http//www.computer.org/csda
  • CSDP Certified Software Development Professional
    (introduced in 2002 for midcareer software
    development practitioners) http//www.computer.or
    g/csdp
  • Both comply with the ISO/IEC 24773 standard
  • ISO/IEC 247732008 is called Software
    EngineeringCertification of Software Engineering
    ProfessionalsComparison Framework
  • uses the IEEE Computer Societys Guide to the
    Software Engineering Body of Knowledge (SWEBOK)
    as its description of the profession

19
SWEBOK
  • Guide to the Software Engineering Body of
    Knowledge (SWEBOK) is the benchmark for defining
    and comparing certifications in software
    engineering, Jim Moore, 2008 chair of the IEEE
    Computer Societys Professional Practices
    Committee, the group that oversees the
    certification programs.
  • http//www.swebok.org/

20
S/W Engineer
  • A good software engineer
  • knows how to identify requirements
  • can properly categorize project risk
  • can accurately estimate
  • These skills are critical to providing customers
    with the correct product, on time, within
    budget. Susan K. (Kathy) Land
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