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GW Chapter 9 Reducing Ambiguity from Start to
Finish Software SpecificationLecture 16

• Prepared by
• Stephen M. Thebaut, Ph.D.
• University of Florida

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The Enemy and The Strategy

• THE fundamental problem of requirements
  definition is ambiguity.
• if we are ever to reduce problem statement
  ambiguity well need tools to slow down the mind,
  tools to prevent us from racing ahead to try
  solving a problem prematurely.

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Heuristics can uncover sources of ambiguity due
to variations in

• Observation what people see or hear of a
  problem (intra-cluster variation).
• Recall what people remember of a problem
  (intra-cluster variation).
• Interpretation how people interpret a problem
  (inter-cluster variation).
• Problem understanding how people define the
  problem in their own mind (inter-cluster
  variation).

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Ambiguity Poll

• Create a metric that requires a solid
  understanding of the problem to estimate.
• Give the problem statement (requirements) to
  informed individuals and ask them to
  independently estimate the value of the metric.
• Bring the individuals together to compare and
  discuss the tabulated results.

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Memorization Heuristic

• Various individuals try to recall the problem
  statement precisely from memory. Parts that are
  not remembered well are likely to be places where
  meaning is not clear.
• A variation is to ask individuals what they
  consider to be the critical parts of the problem
  statement. When the lists are combined and
  discussed, differences reveal potentially
  ambiguous parts.

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Mary had a little lamb Heuristic
Mary had a little lamb.
Mary had a little lamb.
Mary had a little lamb.
Mary had a little lamb.
Mary had a little lamb.
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Mary conned the trader Heuristic
Mary owned a petite lamb.
Mary consumed a small amount of lamb.
Mary had a little lamb.
Mary conned the trader.
Mary was involved with a young sheep.
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Exercises

• Equivalence Partitioning is a black-box test
  case design strategy. Read the description
  provided carefully.

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Exercises

• An operational specification for selecting a
  sub-set of all possible test cases associated
  with a Cause-Effect (black-box) system model is
  provided. Read the specification carefully.

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Exercises (contd)

• Apply the Mary had a little lamb heuristic to
  the statement
• Testing is the process of executing a program
  with the intent of finding errors.
• until as many interpretations as possible are
  discovered.

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Exercises (contd)

• Apply the Mary conned the trader heuristic to
  the statement
• Testing is any activity aimed at evaluating an
  attribute or capability of a program or system.
  It is the measurement of software quality.
• to form additional interpretations.

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Exercises (contd)

• Without discussion and without re-reading the
  Equivalence Partitioning description, write
  down what you consider to be the critical parts
  of the design strategy.
• (When you finish, compare your answers to the
  Equivalence Partitioning description.)

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Exercises (contd)

• Without discussion and without re-reading the
  operational specification for selecting test
  cases for a Cause-Effect system model, estimate
  the number of programmer days that would be
  required to correctly implement a program to
  solve this problem.
• Submit your estimate in class or to the TA, who
  will tabulate and post the results.

Software Specification GW Chapter 9
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GW Chapter 9 Reducing Ambiguity from Start to
Finish Software SpecificationLecture 16

• Prepared by
• Stephen M. Thebaut, Ph.D.
• University of Florida