SOFTWARE QUALITY CONCEPTS - Software Design for Six-Sigma: A Roadmap for Excellence - page 14

Quality can be defined and measured by its attributes. A proposed way that could
be used for measuring software quality factors is given in the following discussion. 6
For every attribute, there is a set of relevant questions. A membership function can
be formulated based on the answers to these questions. This membership function
can be used to measure the software quality with respect to that particular attribute.
It is clear that these measures are fuzzy (subjective) in nature.
The following are the various attributes that can be used to measure software
quality:

1.7.1 Understandability

Understandability can be accomplished by requiring all of the design and user doc-
umentation to be written clearly. A sample of questions that can be used to measure
the software understandability:

Do the variable names describe the functional property represented? (V1)
Do functions contain adequate comments? (C1)
Are deviations from forward logical flow adequately commented? (F1)
Are all elements of an array functionally related? (A1)
Are the control flow of the program used adequately? (P1)

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

µ Understandability = f l(V1 , C1 , F1 , A1 , P1)

1.7.2 Completeness

Completeness can be defined as the presence of all necessary parts of the software
system, with each part fully developed. This means that 7 if the code calls a module
from an external library, the software system must provide a reference to that library
and all required parameters must be passed. A sample of questions that can be used
to measure the software completeness:
The membership function for measuring the software quality with respect to
completeness can be defined as follows:

µ Completeness = f 2(C2 , P2 , S2 , E2)

6 http://en.wikipedia.org/wiki/Software quality.
7 http://en.wikipedia.org/wiki/Software quality.