[SystemSafety] Safety Cases

[nfr]

Michael,

In addressing safety, "wrong" equals "unsafe". And to determine what might be, or might become, unsafe, we need to identify the hazards.

What is right, in that context, is what is deemed not to be unsafe.

Felix.


On 10 Feb 2014, at 11:43, Michael Jackson wrote:

> Felix:
> 
> Yes. But surely there is a missing prior question here:
> 
> 0. What constitutes going right?
> 
> How can we discuss 'going wrong' without a clear understanding of 'going right'?
> Yet in much discussion of safety this question seems to be relegated to a tacit
> background understanding.
> 
> -- Michael Jackson
> 
> 
> At 11:19 10/02/2014, nfr wrote:
> 
>> In the 1980s, 'the safety case' was defined as having the purpose of answering three questions:
>> 
>> 1. What could [possibly] go wrong?
>> 
>> 2. Why won't it?
>> 
>> 3. But what if it did?
>> 
>> One or two of you might propose that each of these questions could be answered by a single sentence. But, with a bit of thought, you'll recognise that, in order to answer the questions fully, a great deal of evidence must be adduced, from a great deal of work - from complete and correct specification, through thorough design, hazard ID, risk assessment, etc., to emergency planning.
>> 
>> Felix.
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>