Software Quality: Definitions and Strategic Issues

In general, software quality is crucial in software engineering. Read this article and explore the various definitions of quality and the quality models. Notice the priority of quality factors and how software quality can be measured.

2. Building quality into software products

2.6. Measuring quality

Gillies (1992) details five approaches to measuring quality from the purchaser's point of view. These are: 

  • Simple scoring 
  • Weighted scoring (or phased weighted factor method) 
  • The Kepner-Tregoe method 
  • The Cologne combination method 
  • Polarity profiling

Because of deficiencies with these methods and because of their older date Gillies suggests a new technique called LOQUM (LOcally defined QUality Modelling) which involves a three step approach:

"LOCRIT: a knowledge elicitation exercise to derive the relevant quality criteria and associated measures.

LOCREL: a further knowledge elicitation to define relationships and conflicts between criteria. 

 LOCPRO: A profiling tool to display a graphical profile to represent the overall quality of the system".

A more scientific approach was proposed by both McCall and by Boëhm. Typical examples are:

Mean Time Between Failure (MTBF)

MTBF = T-tot

N

T-tot = the total time period N = the number of failures in T-tot

Complexity is measured by McCabe (1976) "as a cyclomatic number, based upon graph theory, that seeks to estimate the number of linearly independent paths through a program".

This level of detail is beyond the scope of this paper. Gillies (1992, p40-43) cites numerous references to quality measurement.