1. Prepared by Stephen M. Thebaut, Ph.D. University of Florida
G&W, Chapter 2: Ambiguity in Stating Requirements Software Specification Lecture 7
Prepared by
Stephen M. Thebaut, Ph.D.
University of Florida

2. Software Specification: G&W Chapter 2
So what IS “ambiguity”?
The quality or state of being “ambiguous…”
Ambiguous:
Doubtful or uncertain, especially from obscurity or indistinctness;
Capable of being understood in two or more possible senses.
Software Specification: G&W Chapter 2

3. Sources of Ambiguity Described by Gause & Weinberg
Missing requirements, as in “creating a means for protecting a small group of human beings from the hostile elements of their environment”
Properties of materials
Structure
Functions
Physical environment
Specific hostilities
Social and cultural environment
Software Specification: G&W Chapter 2

4. Sources of Ambiguity Described by Gause & Weinberg (cont’d)
Ambiguous words
Small
Inexpensive
Group
Efficient
User-friendly
Reliable
Introduced elements (unnoticed assumptions)
Software Specification: G&W Chapter 2

5. Software Specification: G&W Chapter 2
Cost of Ambiguity
What are the costs of ambiguity in requirements?
Boehm’s study of relative costs to fix an error (which only considered completed projects)
Other catastrophes:
Ford Pinto
Asbestos building materials
USS Vincenes incident
Software Specification: G&W Chapter 2

6. “Exploring” to Remove Ambiguity
G&W’s picture of requirements
A six-step model of exploration:
Move in some direction.
Look at what they find there.
Record what they find.
Software Specification: G&W Chapter 2

7. “Exploring” to Remove Ambiguity (cont’d)
Analyze their findings in terms of where they want to be.
Use their analysis and recordings of what they find to choose the next direction.
Go back to step 1 and continue exploring.
Software Specification: G&W Chapter 2

8. Is “Ambiguity” Really a 4-Letter Word?
Gause & Weinberg seem to imply this is the case…at least in stating requirements.
Is ambiguity ever desirable?
Politics
International affairs
Commerce
Personal relationships
Software Specification: G&W Chapter 1

9. Prepared by Stephen M. Thebaut, Ph.D. University of Florida
G&W, Chapter 2: Ambiguity in Stating Requirements Software Specification Lecture 7
Prepared by
Stephen M. Thebaut, Ph.D.
University of Florida