Software Engineering for Students A Programming Approach

Summary
The ideal characteristics of a requirements specification are that it is:
■ implementation free
■ complete
■ consistent
■ unambiguous
■ concise
■ minimal
■ understandable
■ achievable
■ testable.
Exercises 47
A number of notations and approaches are available to carry out requirement specification.
The notations range from informal (use case diagrams) through semi-formal
(e.g. use cases) to formal (mathematics).
A useful checklist for the ingredients of a specification is:
1. functional requirements
2. data requirements
3. performance requirements
4. constraints
5. guidelines.
A major vehicle for describing functional requirements are use cases and UML use
case diagrams. A use case is a textual description of a small, but complete user task.
A use case diagram shows all the actors and all the use cases for a system.
The main issue with specifications is good communication, both in discussions and
in writing.
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Exercises
4.1 Appendix A gives specifications for several systems. For each specification identify
the functional, data and performance components of the specification. Use the guidelines
and checklists given above to rewrite and thereby improve the specification.
4.2 Appendix A gives specifications for several systems. For each specification identify and
write the use cases. Draw a use case diagram.