[SystemSafety] Proven use software and software quatitative reliability

From: RICQUE Bertrand (SAGEM DEFENSE SECURITE) < >
Date: Fri, 13 Mar 2015 15:07:27 +0100


The normal framework in system + SW production (as well under IEC61508 as ARP/DO) is:

· Assign a DAL/SIL

· According to this DAL/SIL comply with requirements

· The SW is then deemed to be compliant with this DAL/SIL and possess the associated properties

· The system also at another level

Some remarks on this framework:

· There are lot of requirements

· Probability of failure is only one among others

· Integrity is an important property

· Probability is (almost) the single one which is not required for SW

Framework for proven in use :

· Observe the system including the SW as a package

· Count the failures

· Extrapolate a probability of failure / reliability FOR the SW alone

· Deduct the guaranteed DAL/SIL

I wonder in which metaclass of fallacies enters this reasoning.

How can one deduct properties of a SW by observing AT SYSTEM LEVEL a parameter which is the single one that is not a design parameter of the said software ?

Bertrand Ricque

Program Manager

Optronics and Defence Division

Sights Program

Mob : +33 6 87 47 84 64

Tel : +33 1 58 11 96 82

Bertrand.ricque_at_xxxxxx

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systemsafety_at_xxxxxx Received on Fri Mar 13 2015 - 15:08:19 CET

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