[SystemSafety] Does "reliable" mean "safe" and or "secure" or neither?

[Coq, Thierry]

Hi
I find this list hugely informative. In particular, I find PBL's posts factual, useful, interesting and intriguing.  As well as the many other debaters who agree with him or challenge him. As it should be. I wish to express my gratitude to all debaters.

However, this last exchange seems to me a debate on authority.
On our left, we have DO-178. B now C.
On our right, we have IEC, IEEE, Musa, etc.

To go further, it is plain fact that the aeronautics industry has demonstrated it doesn't need "software reliability" to deliver highly reliable automated systems, or systems of systems.
It seems evident with the knowledge we have of the aeronautics success that in order to use "software reliability" in other industries, or in aeronautics, there needs to be a clear use case where the value of "software reliability" is demonstrated, compared to other methods or techniques, in order to apply "software reliability". The analogy of software and hardware does not seem valid, as software does not "fatigue" or randomly "break" the way hardware does, which is the basis for all probabilistic reliability theories for hardware. The analogy that does seem valid between hardware and software is the presence of systematic faults, in design, manufacturing, installation, testing, misuse, etc. Which in hardware also does not have a probability number. Formal methods can be used to identify such systematic faults in software. If one can be found, then a test environment can be devised in which the software will fail 100% of the time. Random hardware faults do not behave like that.

Best regards,
Thierry Coq
The opinions reflected here are my own and are not necessarily those of my employer

-----Original Message-----
From: systemsafety [mailto:systemsafety-bounces at lists.techfak.uni-bielefeld.de] On Behalf Of Peter Bernard Ladkin
Sent: dimanche 24 avril 2016 03:27
To: The System Safety List
Subject: Re: [SystemSafety] Does "reliable" mean "safe" and or "secure" or neither?

On 2016-04-23 19:43 , Nick Tudor wrote:
> DO-178C

In the absence of a complete sentence, let me suggest one.

---- DO178C sees no need to assign any meaning to the term "software reliability".

It's fine for some industry consortium to find it has no use for a specific concept. RTCA likely has no use for the notion of a cup of tea, either (BS6008). But that doesn't mean it makes any sense to argue that there isn't any such thing as a cup of tea.

PBL

Prof. Peter Bernard Ladkin, Faculty of Technology, University of Bielefeld, 33594 Bielefeld, Germany Je suis Charlie
Tel+msg +49 (0)521 880 7319  www.rvs.uni-bielefeld.de






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