SOFTWARE QUALITY CONCEPTS - Software Design for Six-Sigma: A Roadmap for Excellence - page 19

Does the software protect itself and its data against unauthorized access and use? (A12)
Does it allow its operator to enforce security policies? (S12)
Are security mechanisms appropriate, adequate, and correctly implemented? (M12)
Can the software withstand attacks that can be anticipated in its intended environment?
(W12)
Is the software free of errors that would make it possible to circumvent its security
mechanisms? (E12)
Does the architecture limit the potential impact of yet unknown errors? (U12)

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

µ Security = f12(A12 , S12 , M12 , W12 , E12 , U12)

There are many perspectives within the field on software quality measurement.
Some believe that quantitative measures of software quality are important. Others
believe that contexts where quantitative measures are useful are they rare, and so
prefer qualitative measures. 9 Many researchers have written in the field of software
testing about the difficulty of measuring what we truly want to measure (Pressman,
2005, Crosby, 1979).
In this section, the functions f1 through f12 can be linear or nonlinear functions.
They can be fuzzy measures. The function f i can be a value within the unit interval
( f i € [0,1]),where f i = 1 means that the software quality with respect to the attribute

i is the highest, and f i = 0 means that the software quality with respect to the attribute
i is the lowest; otherwise the software quality will be relative to the value of f i.

1.8 SUMMARY

Quality is essential in all products and systems, and it is more so for software systems
because modern computer systems do execute millions of instructions per second,
and a simple defect that would occur once in a billion times can occur several times
a day.
High-quality software would not only decrease cost but also reduce the production
time and increase the company's competence within the software production world.
Achieving a high quality in software systems demands changing and improving
the process. An improved process would include defining the quality goal, measuring
the software product quality, understanding the process, adjusting the process, using
the adjusted process, measuring the results, comparing the results with the goal, and
recycling and continue improving the process until the goal is achieved. It also can
be achieved by using DFSS as will be discussed in the following chapters.

9 http://en.wikipedia.org/wiki/Software quality.