ch10-FormalSpecification

ch10-FormalSpecification - 1 Formal Specification Chapter...

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Unformatted text preview: 1 Formal Specification Chapter 10 2 Topics covered l Formal specification in the software process l Sub-system interface specification l Behavioural specification 3 Formal methods l Formal specification is part of a more general collection of techniques that are known as formal methods. l These are all based on mathematical representation and analysis of software. l Formal methods include Formal specification; Specification analysis and proof; Transformational development; Program verification. 4 Acceptance of formal methods l Formal methods have not become mainstream software development techniques as was once predicted Other software engineering techniques have been successful at increasing system quality. Hence the need for formal methods has been reduced; Market changes have made time-to-market rather than software with a low error count the key factor. Formal methods do not reduce time to market; The scope of formal methods is limited. They are not well-suited to specifying and analysing user interfaces and user interaction; Formal methods are still hard to scale up to large systems. 5 Use of formal methods l The principal benefits of formal methods are in reducing the number of faults in systems. l Consequently, their main area of applicability is in critical systems engineering. There have been several successful projects where formal methods have been used in this area. l In this area, the use of formal methods is most likely to be cost-effective because high system failure costs must be avoided. 6 Specification in the software process l Specification and design are inextricably intermingled. l Architectural design is essential to structure a specification and the specification process. l Formal specifications are expressed in a mathematical notation with precisely defined vocabulary, syntax and semantics. 7 Specification and design 8 Specification in the software process 9 Use of formal specification l Formal specification involves investing more effort in the early phases of software development. l This reduces requirements errors as it forces a detailed analysis of the requirements. l Incompleteness and inconsistencies can be discovered and resolved. l Hence, savings as made as the amount of rework due to requirements problems is reduced . 10 Cost profile l The use of formal specification means that the cost profile of a project changes There are greater up front costs as more time and effort are spent developing the specification. However, implementation and validation costs should be reduced as the specification process reduces errors and ambiguities in the requirements. 11 Development costs with formal specification 12 Specification techniques l Algebraic specification The system is specified in terms of its operations and their relationships....
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ch10-FormalSpecification - 1 Formal Specification Chapter...

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