Littlewood, B. & Povyakalo, A. A. (2012). Conservative bounds for the pfd of a 1outof2 softwarebased system based on an assessor’s subjective probability of "not worse than independence" (Report No. CSR Technical Report, 20 May 2012). London: Centre for Software Reliability, City University London.
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Abstract
We consider the problem of assessing the reliability of a 1outof2 softwarebased system, in which failures of the two channels cannot be assumed to be independent with certainty. An informal approach to this problem assesses the channel pfds (probabilities of failure on demand) conservatively and then multiplies these together in the hope that the conservatism will be sufficient to overcome any possible dependence between the channel failures. Our intention here is to place this kind of reasoning on a formal footing. We introduce a notion of “not worse than independence” and assume that an assessor has a prior belief about this, expressed as a probability. We obtain a conservative prior system pfd, and show how a conservative posterior system pfd can be obtained following the observation of a number of demands without system failure. We present some illustrative numerical examples, discuss some of the difficulties involved in this way of reasoning, and suggest some avenues of future research.
Item Type:  Report 

Subjects:  Q Science > QA Mathematics > QA76 Computer software 
Divisions:  School of Informatics > Centre for Software Reliability 
URI:  http://openaccess.city.ac.uk/id/eprint/1612 
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 Conservative bounds for the pfd of a 1outof2 softwarebased system based on an assessor’s subjective probability of "not worse than independence". (deposited 25 Sep 2012 14:26) [Currently Displayed]
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