Object-Oriented Software Development with UML - UNU-IIST ...

Evolutionary Development 11RequirementAnalysisDesignImplementationand Unit TestingIntegrating andSystem TestingOperation andMaintenanceFigure 2.5: The Waterfall ModelThe waterfall model can be used for some statistic studies about the software development. Figure 2.6and Figure 2.7 illustrate why high quality software is difficult to produce and to maintain, and why thedevelopment activities must be conducted in a good engineering manner.2.3 Evolutionary DevelopmentA problem with the waterfall model is that some software development project is difficult to be partitionedinto the distinct stages of requirement analysis, design and so on. Sometimes, it is also difficult (or impossible)to establish a detailed requirement specification.Evolutionary development is based on the idea of developing an initial implementation, exposing this touser comment and refine through many versions until an adequate system has been developed (Figure 2.8).The development process starts with an outline description of the system. Rather than having separatespecification, development (design, implementation) and validation (testing and/or verification and/or prototyping)activities, these are carried out concurrently with rapid feedback across these activities.The techniques used in an evolutionary development include¢Exploratory programming where the objective of the process is to work with the client to exploretheir requirements and deliver a final system. The development starts with the parts of the systemwhich are understood. The system evolves by adding new features as they are proposed by the client.Prototyping where the objective of the development is to understand the customer’s requirements¢Report No. 259, July 2002UNU/IIST, P.O. Box 3058, Macau