An extended model for cost of software quality
22.3 An extended model for cost of software quality
Analysis of the software quality costs defined by the classic model reveals that several costs of substantial magnitude are excluded. These costs are either unique to the software industry or negligible for other industries. For example, typical software quality failure costs include:
Damages paid to customers as compensation for late completion of the project due to unrealistic scheduling
Damages paid to customers in compensation for late completion of the project as a result of failure to recruit sufficient staff.
The element common to these two failures is that they result not from any particular action of the development team or any lack of professionalism; they are actually outcomes of managerial failure.
Management can perform several activities to prevent or reduce the costs that result from the types of failure particular to its functions:
Contract reviews (proposal draft review and contract draft review). The cost of these reviews is usually negligible for contracts in the manufac- turing industries. However, in the software industry, considerable
456 professional work is required to assure that a project proposal is based on sound estimates and comprehensive evaluations. The significant dif-
22 ference in required resources results from the nature of the product and
C the production process covered by the contract. While a typical contract o
sts in the manufacturing industry deals with repeated manufacturing of cat-
alog-listed products, a typical contract in the software industry deals with
of
development of a new, unique software system (see Chapter 1).
softw
Thorough appropriate progress control of the software project. While production control carried out in the manufacturing industry is a repeti-
are quality
tive task that can, in most cases, be performed automatically by machines, software development progress control supervises task design and coding activities performed for the first time by the development team.
The important effect of management on the cost of software quality is reflect-
ed by the title of Flowers’ book: Software Failure: Management Failure (Flowers, 1996). In this book Flowers describes and analyzes several colossal software project failures; he concludes by discussing the critical managerial failures at their root and suggests ways to prevent or reduce them.
The extended cost of software quality model, as proposed by the author of this volume, extends the classic model to include management’s “contri- butions” to the total cost of software quality. According to the extended model, two subclasses are added to complete the model’s coverage: manage- rial preparation and control costs, and managerial failure costs. The extended cost of software quality model is shown in Figure 22.2. In the sec- tions below, the new cost subclasses are discussed in full.
Prevention costs
costs Managerial preparation
and control costs Cost of
software quality Internal
failure costs
Failure of
External
control costs
failure costs Managerial
failure costs Figure 22.2: The extended cost of software quality model
22.3.1 Managerial preparation and control costs 457 Managerial preparation and control costs are associated with activities per-
22.3 An extended model
formed to prevent managerial failures or reduce prospects of their occurrence. Several of these activities have already been discussed in previ- ous chapters related to various SQA frameworks. Typical managerial preparation and control costs include:
Costs of carrying out contract reviews (proposal draft and contract draft reviews) – see Chapter 5.
Costs of preparing project plans, including quality plans and their review – see Chapter 6.
Costs of periodic updating of project and quality plans.
for c
Costs of performing regular progress control of internal software devel- opment efforts – see Chapter 20.
st of
Costs of performing regular progress control of external participants’
contributions to the project – see Chapter 12.
softw