NO SILVER BULLETS-Fredrick Brooks

1. NO SILVER BULLET
Essence and Accident in
Software Engineering
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2. Frederick Phillips Brooks JR
Education: Duke University 1953
Havard University 1956
Fields: CS, OS, SE
Achievements: OS/360
“The Mythyical Man-Month”
Awards&Honours: IEEE Virtual Reality
Career Award(2010)
And more than 25
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“There is no single development, in
either technology or management
technique, which by itself promises
even one order of magnitude
improvement within a decade in
productivity, in reliability, in
simplicity.”

4. What are werewolves and
Silver Bullets?
• Werewolves:
Human with the ability to shape shift into a
wolf.
Popular movie topic.
Oldest monster legend.
• Silver Bullet(or a magical bullet):
The only thing that can kill werewolves.
Movie name (Horror 1985).
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5. Essence:
The most basic and important quality
of something.
Accident:
Those difficulties that today attend its
production but that are not inherent.
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6. All software involves essential difficulties and
accidental difficulties.
ESSENTIAL DIFFICULTIES:
• Software, as its core has these essential
difficulties.
I. Complexity
II. Conformity
III. Changeability
IV. Invisibility
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ESSENTIAL DIFFICULTIES AND
ACCIDENTAL DIFFICULTIES:

7. Software is much more complex than any other human
construct.
Problems caused:
Technical:
• Decrease of reliability, extensibility, safety.
Management:
• Difficulty of communication between team members.
• Difficulty of invoking function-makes programs hard to use.
• Complexity of structure brings the difficulty of extending
programs to new functions without creating side effects. 7
COMPLEXITY:

8. CONFORMITY:
 Software has to be made to agree to common
interface, protocols, standards etc.
 Mostly standards for mastering complexity is
arbitrary. Human institutions and systems must
conform these standards and interface and they
differ from:
• Interface to interface.
• Time to time.
• Designed by different people.
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9. CHANGEABILITY:
Software entity is constantly
subject to pressure for change.
All successful software get
changed.
Change comes in two ways:
• People use the software in ways not
originally foreseen in the design and
want better support for that
• The physical machine/OS changes
underneath us.
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10. INVISIBLITY:
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 Software is invisible and unvisualisable.
It is also very difficult even to visualize since
there are many ways to look at the same design:
“the reality of software is not inherently
embedded in space.”
This inhibits communication of structure and
design.

11. PAST BREAKTHROUGHS SOLVED
ACCIDENTAL DIFFICULTIES:
 The accidental qualities are all
about implementation and testing,
and these have been solved almost
as well as they are likely to be
solved, so don’t expect many more
breakthroughs.
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High level languages:
High level languages allow programmers to
express implementation with concepts closer to that
which we use in design.
Unified Programming Environment:
Unified Programming Environment enable related
individual tools to work together in an automatic manner.
Time Sharing:
Timesharing eliminates the slow turnaround of
batch programming and keeps fresh in mind the grasp of
complex system.

13. HOPE FOR SILVER:
Is there any potential solution now a days?
 Ada and other high-level language advances?
 Object-oriented programming?
 Artificial Intelligence?
 Expert System?
 Automatic Programming?
 Graphical Programming?
 Program Verification?
 Environment and Tools?
 Workstation?
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Ada & other High-Level Language Advances:
One of the most touted development, not only reflects
evolutionary improvements in language concepts but
personify features to encourage modern design.
It is just another high level language but no proved to be
a silver bullet.
Object Oriented Programming:
It is a programming language model organized around
objects rather than "actions" and data rather than logic.
Has two classes:
Abstract data types.
Hierarchical types.

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Artificial
Intelligence:
Revolutionary breakthrough
Parnas has clarified the terminological
choas:
AI-1: The use of computers to solve
problems that previously could only be
solved by applying HI.
AI-2: The use of a specific set of
programming techniques knows as heuristic
or rule based programming.

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Expert System:
A program containing a
generalized interface
engine and rule base, takes
input data and
assumptions, explore the
inferences derivable from
the rule base, yields
conclusion and advice and
explains its results by
retracting its reasoning for
the user.

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Automatic Programming:
“Automatic programming always has
been a euphemism for programming
with a higher level language than was presently
available to the programmer”
Graphical Programming:
Computer graphics which has been
applied successfully in other fields, seems to be
able to play a role in software design.
Program Verification:
Program verification seems promising to avoid
immense effort upon implementation and testing
by eliminating errors in design phase.

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Environment and tools:
 The general pain of all these tools and environments is
remembering to use them…
 For example, configuration management systems depend on
programmers’ checking modules out for working on them and
on programmers’ checking modules back in when the
programmers are finished with working on them.
 When a programmer fails to check a module out, check a
module back in, or to meet with another, the system loses
control and the completeness and consistency it promises
cannot be guaranteed any more.
Workstation:
• More powerful computers surely
facilitate software development.

19. Promising Attacks on the Essence
Buy versus build:
• In the mid 1980s, the software market
was still small. The market is becoming
large enough. So, Don't develop
software when you can avoid it.
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Requirements Refinement and Rapid
Prototyping:
 Helps decide what to build
 Use to clarify requirement
 A means to identify requirements, to try out various
ideas, to do usability testing,etc
 To the extent that it succeeds, it delays and
moderates the B-L upswing.
 Make the new software system work like our old
manual information-processing system.

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Great designers:
Be on the look out for them, when you find them,
don't let go!
some people are just better at software design than
others. Try to identify them, keep in mind them in
your organization, and spoil them so that they get
the skills and recompense that they need.
Incremental development-grow,
not building, software:
 This helps to upgrade requirements, prove the
design, and improves optimism.
 Don't build software, grow it. The same benefits
can be realized on large projects as on my small
ones.

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