1. G&W Chapter 14: Functions Software Specification Lecture 21
Prepared by
Stephen M. Thebaut, Ph.D.
University of Florida

2. Software Specification: G&W Chapter 14
What are Functions?
They describe the what of a product; i.e., what the product is to accomplish.
They are verbs representing actions for which the product is the subject.
Software Specification: G&W Chapter 14

3. What are Functions? (cont’d)
To test whether a requirement is a function, put the phrase “We want the product to…” or “The product should…” in front of it. E.g.,
The product should update pending orders daily.
The product should user friendly.
Software Specification: G&W Chapter 14

4. What is the “exists” function?
The highest level (i.e., “first”) function of any product, as in: We want the product to exist.
Questions to kick-start the sub-function brain-storming process for the “exists” function:
What is the purpose of this product?
How would you / others like to use this product?
Don’t worry about how much it would cost / whether it can really be done. What would you like?
Software Specification: G&W Chapter 14

5. What are EVIDENT and HIDDEN Functions?
Evident (E) functions: those to be performed in a manner that is as visible or evident to users as possible.
Hidden (H) functions: those to be performed in a manner that is as imperceptible to users as possible.
Software Specification: G&W Chapter 14

6. What are FRILL (“Get it if You Can”) Functions?
Frill (F) functions: those that the client would like, but not if they cost anything, either directly or in compromises with other functions.
Software Specification: G&W Chapter 14

7. Heading for the Frill Function List
“The designers will be alert to opportunities to provide these functions whenever they can do so without trading away other functions or attributes to get them.”
Putting frill functions on a wish list can defuse arguments over keeping or discarding some-one’s favorite idea.
Software Specification: G&W Chapter 14

8. Other Possible Classifications
Translucent (T) functions: those to be performed in a manner that is vague but not imperceptible to users.
Opaque (O) functions: those for which their existence must not be known by certain user constituencies.
Software Specification: G&W Chapter 14

9. Function Identification Heuristic
For each cycle of function refinement, starting with the “exists” function, perform these steps:
Have the client brainstorm all conceivable (sub-) functions.
Classify each function as evident, hidden, or frill.
Try to uncover additional hidden functions, perhaps with another brainstorming.
Software Specification: G&W Chapter 14

10. Function Identification Heuristic (cont’d)
Identify functions with implied solutions and transform the wording to become problem statements rather than solution statements.
Create a “Get it if You Can” list for the frill functions.
Software Specification: G&W Chapter 14

11. Software Specification: G&W Chapter 14
Exercise
A client has brainstormed the list of “functions” below for a device to tell time.
Which are functions and which are attributes?
Are there any implied solutions?
How might the client classify the functions as Evident, Hidden, or Frill?
Software Specification: G&W Chapter 14

12. Software Specification: G&W Chapter 14
Exercise (cont’d)
Keep time
Display current time to user
Indicate when a user specified time occurs
Portable
Adjust to different time zones
Appear to be jewelry-like when desired
Function in most weather conditions
Software Specification: G&W Chapter 14

13. G&W Chapter 14: Functions Software Specification Lecture 21
Prepared by
Stephen M. Thebaut, Ph.D.
University of Florida