[SystemSafety] "Security Risk" and Probability

[Palin, Stuart (UK)]

From: Peter Bernard Ladkin <ladkin at causalis.com>
To: systemsafety at lists.techfak.uni-bielefeld.de
...
> What seems a little harder to construct is an example of software which is safe
> (that is, implements a safety function per requirement) but may be made to
> violate availability. Anyone?

This seems to be taking a very narrow view of what constitutes "safe software".

Consider an advisory system - its safety requirement might be that it does not provide misleading advice.  If it does not provide advice that is OK as it is not misleading.

This is often a feature of display systems - displaying wrong information is a safety concern, occluding the display because the information is known to be suspect, or the display simply going off, is not a safety concern; thus availability is not necessarily a safety concern.

[I thought that in years past you had addressed this in establishing a distinction between reliability and safety!!]

Stuart

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