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Subjective Safety Analysis of Safety Requirements Specifications

Lookup NU author(s): Dr Amer Saeed, Dr Rogerio De Lemos



This report presents a method for subjective safety analysis of safety requirements specifications of software for safety-critical systems, that are organised in an hierarchical structure. The methodology incorporates fuzzy set modelling and evidential reasoning to assess the safety associated with safety requirements specifications. Fuzzy set theory is used to model the primitive elements (i.e. safety rules) of the requirements specifications and an evidential reasoning approach is employed to synthesize the information produced. Three basic parameters - failure likelihood, consequence severity and failure consequence probability are used to analyse a safety rule in terms of membership functions. The subjective safety description associated with the safety rule is then mapped back to the defined safety expressions which are also characterised in terms of membership functions. Such a mapping results in the production of the safety evaluation associated with the safety rule, expressed in terms of the degrees to which the subjective safety description belongs to the safety expressions. Such degrees represent uncertainty in the safety evaluation associated with the safety rule. The information produced for all safety rules can then be synthesized using an evidential reasoning approach to obtain the safety evaluation associated with the safety requirements specifications. The developed method is capable of dealing with multiple safety analysis who make judgements on each safety rule. A case study based on a train set crossing is used to demonstrate the method.

Publication metadata

Author(s): Wang J, Saeed A, de Lemos R

Publication type: Report

Publication status: Published

Series Title: Department of Computing Science Technical Report Series

Year: 1997

Pages: 36

Print publication date: 01/06/1997

Source Publication Date: June 1997

Report Number: 569

Institution: Department of Computing Science, University of Newcastle upon Tyne

Place Published: Newcastle upon Tyne