chap27 - Chapter 27 Formal Specification Chapter 27 Formal...

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Chapter 27 Formal Specification Slide 1 Chapter 27 Formal Specification
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Chapter 27 Formal Specification Slide 2 Objectives To explain why formal specification helps discover problems in system requirements . To describe the use of: Algebraic specification techniques, and Model-based specification techniques (including simple pre- and post-conditions). And to introduce Function-based program specification.
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Chapter 27 Formal Specification Slide 3 Formal methods Formal specification is part of a more general collection of techniques known as “formal methods .” All are based on the mathematical rep- resentations and analysis of requirements and software.
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Chapter 27 Formal Specification Slide 4 Formal methods (cont’d) Formal methods include: Formal specification Specification analysis and property proofs Transformational development Program verification (program correctness proofs) Specifications are expressed with precisely defined vocabulary, syntax, and semantics. (e.g., “model checking”) (axiomatic, function theoretic)
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Chapter 27 Formal Specification Slide 5 Acceptance and use Formal methods have not become mainstream as was once predicted, especially in the US. Some reasons why: 1. Less costly techniques (e.g., inspections / reviews) have been successful at increasing system quality. (Hence, the need for formal methods has been reduced.) (cont’d )
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Chapter 27 Formal Specification Slide 6 Acceptance and use (cont’d) 2. Market changes have made time-to- market rather than quality the key issue for many systems. (Formal methods do not reduce time-to-market.) 3. Limited scope of formal methods . They’re not well-suited to specifying user interfaces. (Many interactive applications are “GUI-heavy” today.) (cont’d )
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Chapter 27 Formal Specification Slide 7 Acceptance and use (cont’d) 4. Formal methods are hard to scale up for very large systems. (Although this is rarely necessary.) 5. Start-up costs are high. 6. Thus, the risks of adopting formal methods on most projects are perceived to outweigh the benefits .
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Chapter 27 Formal Specification Slide 8 Acceptance and use (cont’d) However, formal specification is an excellent way to find (at least some types of) require- ments errors and to express requirements unambiguously . Projects which use formal methods invariably report fewer errors in the delivered software. (cont’d )
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Chapter 27 Formal Specification Slide 9 Acceptance and use (cont’d) In systems where failure must be avoided, the use of formal methods is justified and likely to be cost-effective . Thus, the use of formal methods is increasing in critical system development where safety, reliability, and security are important.
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Chapter 27 Formal Specification Slide 10 Formal specification in the software Requirements specification Formal specification System modelling Architectural design Requirements High-level elicitation a “back - end” element of requirements elicitation/analysis/specification/validation
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Chapter 27 Formal Specification Slide 11
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This note was uploaded on 05/27/2011 for the course CEN 5035 taught by Professor Staff during the Fall '08 term at University of Florida.

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chap27 - Chapter 27 Formal Specification Chapter 27 Formal...

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