Software Engineering for Students A Programming Approach

Pitfalls
For users, the problems of prototyping are:
23.7 Discussion 311
■ because prototyping is carried out in an artificial environment, users may miss some
of the shortcomings
■ undue user expectations – the ability of the developers to create a prototype quickly
may raise undue expectations that the final system will soon be complete. They
see a partial system and may not understand that it is not the finished system
■ inconsistencies between a prototype and the final system – if the prototype is a
throwaway, the end product may not be exactly like the prototype. In other words,
what the user sees may not be what the user gets
■ users who are never satisfied because they are given too much opportunity to
change the development of the system.
For software engineers, the problems can be:
■ incomplete analysis – because prototypes are produced quickly, developers may be
tempted to plunge into prototyping before sufficient requirements analysis has
taken place. This may result in a system that has a good user interface but is not
properly functional. This is how the reputation of prototypes which are quick but
dirty came about.
■ iteration is not easily accepted by some designers, because it necessitates discarding
their own work
■ omission of non-functional requirements, since a prototype focuses only on functionality.
The project management problems of using prototyping may be:
■ estimating, planning and managing a prototyping project can be difficult because it
can be hard to predict how many iterations of prototyping will take place
■ procedures for change and configuration management may be unsuitable for controlling
the rapid change inherent in prototyping
■ many project management structures are set up assuming a process model, like the
waterfall model, that generates regular deliverables to assess progress. However,
prototypes usually evolve so quickly that it is not cost effective to keep pace with the
documentation.
Maintenance of a system constructed using evolutionary prototyping can be difficult
and costly because continual change tends to corrupt the structure of the prototype.
Prototyping may not always be an appropriate technique, for example, in:
■ embedded software
■ real-time control software
■ scientific and engineering numerical computational software.