Re: [sc] A Suggestion on Ensuring Safety Requirements Fulfilment even if your SW is imperfect



Re: [sc] A Suggestion on Ensuring Safety Requirements Fulfilment even if your SW is imperfect

From: Nancy Leveson <leveson.nancy8_at_xxxxxx>
Date: Sun, 16 Oct 2011 05:09:40 -0700
Message-ID: <CABMQRd4XRRPEmRtL9LHPBhXLbh_4GM33vHOtbcQXGGpzcm-KFw@xxxxxx>
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Peter, I must not be understanding something here. You write at the end:

*"However, in such a case I suspect very much that the software should be
redesigned to ensure the avoidance of H. Since H is a SW state, I see no
reason why this should not be generally possible."*
*
*
If it is possible to redesign the software to avoid the hazard, why wouldn't
you always do this? The first step is system engineering is to identify the
requirements, including safety requirements (constraints). Once the
requirements for safety are identified, the "design precedence" for safe
design is to try to eliminate the hazard. The next is to avoid the hazard.
Reacting to the hazard and trying to reverse it or eliminate its bad effects
is way down on the precedence level.

Nancy
*
*
*
*
On Sun, Oct 16, 2011 at 2:23 AM, Peter Bernard Ladkin <
ladkin@xxxxxx> wrote:

> http://www.**abnormaldistribution.org/2011/**10/16/ensuring-safety-**
> requirements-fulfilment-in-**possibly-imperfect-software/<http://www.abnormaldistribution.org/2011/10/16/ensuring-safety-requirements-fulfilment-in-possibly-imperfect-software/>
>
> PBL
>
> Peter Bernard Ladkin, Professor of Computer Networks and Distributed
> Systems,
> Faculty of Technology, University of Bielefeld, 33594 Bielefeld, Germany
> Tel+msg +49 (0)521 880 7319  www.rvs.uni-bielefeld.de
>
>
>
>
>
>


-- 
Dr. Nancy Leveson
Professor, Aeronautics and Astronautics
Professor, Engineering Systems
MIT

http://sunnyday.mit.edu

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Received on Sun 16 Oct 2011 - 13:09:47 BST