SOFTWARE QUALITY CONCEPTS - Software Design for Six-Sigma: A Roadmap for Excellence - page 16

1.7.5 Consistency

Consistency means the uniformity in notation, symbols, appearance, and terminology
within the software system or application. A sample of questions that can be used to
measure the software consistency:

Is one variable name used to represent different logical or physical entities in the program?
(V5)
Does the program contain only one representation for any given physical or mathematical
constant? (P5)
Are functionally similar arithmetic expressions similarly constructed? (F5)
Is a consistent scheme used for indentation, nomenclature, the color palette, fonts and other
visual elements? (S5)

The membership function for measuring the software quality with respect to
consistency can be defined as follows:

µ Consistency = f 5(V5 , P5 , F5 , S5)

1.7.6 Maintainability

Maintainability is to provide updates to satisfy new requirements. A maintainable
software product should be well documented, and it should not be complex. A
maintainable software product should have spare capacity of memory storage and
processor utilization and other resources. A sample of questions that can be used to
measure the software maintainability:

Has some memory capacity been reserved for future expansion? (M6)
Is the design cohesive (i.e., does each module have distinct, recognizable functionality)?
(C6)
Does the software allow for a change in data structures? (S6)
Is the design modular? (D6)
Was a software process method used in designing the software system? (P6)

The membership function for measuring the software quality with respect to
maintainability can be defined as follows:

µ Maintainability = , , , ,

f 6(M6 C6 S6 D6 P6)

1.7.7 Testability

A software product is testable if it supports acceptable criteria and evaluation of per-
formance. For a software product to have this software quality, the design must not be
complex. A sample of questions that can be used to measure the software testability: