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2.3 Coping with change 49

Determine Objectives, Evaluate Alternatives,
Alternatives, and Identify, Resolve Risks
Constraints
Risk
Analysis
Risk
Analysis
Risk
Analysis Operational
Prototype 3 Prototype
Prototype 2
Risk
Analysis Proto-
REVIEW type 1
Simulations, Models, Benchmarks
Requirements Plan
Life-Cycle Plan Concept of
Operation
S/W
Requirements Product
Design Detailed
Requirement Design
Development Validation Code
Plan
Unit Test
Integration Design Integration
and Test Plan V&V
Plan Next Phase Test
Acceptance
Test
Service Develop, Verify
Next-Level Product
changes are a result of project risks and includes explicit risk management activities
Figure 2.11 Boehm’s
spiral model of the to reduce these risks.
software process Each loop in the spiral is split into four sectors:
(©IEEE 1988)
1. Objective setting Specific objectives for that phase of the project are defined.
Constraints on the process and the product are identified and a detailed manage-
ment plan is drawn up. Project risks are identified. Alternative strategies,
depending on these risks, may be planned.
2. Risk assessment and reduction For each of the identified project risks, a detailed
analysis is carried out. Steps are taken to reduce the risk. For example, if there is a
risk that the requirements are inappropriate, a prototype system may be developed.

3. Development and validation After risk evaluation, a development model for the
system is chosen. For example, throwaway prototyping may be the best devel-
opment approach if user interface risks are dominant. If safety risks are the main
consideration, development based on formal transformations may be the most
appropriate process, and so on. If the main identified risk is sub-system integra-
tion, the waterfall model may be the best development model to use.

4. Planning The project is reviewed and a decision made whether to continue with
a further loop of the spiral. If it is decided to continue, plans are drawn up for the
next phase of the project.