Software Engineering for Students A Programming Approach

366 Chapter 29 ■ Software metrics and quality assurance
used for documenting module specifications. After any changes have been made, measurements
are continued, and the search goes on for further improvements. Deming
suggests that improvements can continue to be made indefinitely.
Deming argues that quality improvements of this type benefit everyone:
■ workers, because they can take control and pride in their work
■ organizations, because they can make increased profits
■ customers, because they get better quality.
29.8 ● The Capability Maturity Model
The Capability Maturity Model (CMM) is a grading system that measures how good an
organization is at software development. This scheme specifies five levels, ranging from
level 1 (bad) to level 5 (good). An organization’s ranking is determined by questionnaires
administered by the Software Engineering Institute of Carnegie Mellon University, USA.
The levels are:
■ Level 1, initial – the development process is ad hoc and even, occasionally, chaotic.
Few processes are defined and the success of any project depends on effort by
individuals. Thus the organization survives through the actions of individual
heroes and heroines who help ensure some success in spite of the way that the
organization is run.
■ Level 2, repeatable – basic project management processes are established within the
organization to track cost, schedule and functionality. The processes enable the
organization to repeat its success obtained with earlier, similar applications.
■ Level 3, defined – the development process for both management and software engineering
activities is documented, standardized and integrated into an organizationwide
development process. All projects use an approved and documented version of
the standard process. This level includes all the characteristics defined for level 2.
■ Level 4, managed – detailed measures of the development process and of the software
product are collected. Both are quantitative and measured in a controlled
fashion. This level includes all the characteristics defined for level 3.
■ Level 5, optimizing – measurements are continuously used to improve the process.
New techniques and tools are used and tested. This level includes all the characteristics
defined for level 4.
Any particular development organization will typically use a mix of good and bad
practice and so the level achieved is the average for the organization. An organization
with a good rating can clearly advertise the fact to get increased business. If an organization,
or individual, is buying or commissioning software, it is clearly better to buy
from a CMM level 5 software development organization, who will probably supply
better software and not necessarily at a more expensive price. Indeed, the evidence is
that an organization that uses better methods achieves higher quality software at a
lower cost.