I shall relay this in an analogy from the mechanical world.
The humble nut and bolt are a pair of components that, according to their data-sheet will exist in a specific environment and be able to be tightened up to a specific toque figure to serve throughout its designated lifetime.
We can use the nut and bolt in a more complex assembly (such as a carburettor for a car) which will perform as indicated in the manufacturers data-sheet as part of the engine component.
The emergent behaviour and failure modes become known through the design process and with the inspection and testing that ensures the final product is as described. Using only certified components and frequent review stages throughout the design keeps the behaviour (designed or emergent) within bounds.
The entire system (the car) is designed around a multitude of components (probably all selected from a catalogue of components that have proven themselves over time).
Note that this analogy is based on vehicle manufacturing before electronics or software became involved. The question I always pose is why electronics and software could not be as certain in its development as those early vehicle designs.
I know it is possible as my electronics and software have survived with zero maintenance effort for more than 20 years (one software system is now operational since 1985 and has just had operational life extension granted until 2030) within very harsh operational environments.
Regards
Paul E. Bennett IEng MIET
Systems Engineer
-- ******************************************************************** Paul E. Bennett IEng MIET.....<email://Paul_E.Bennett_at_xxxxxx Forth based HIDECS Consultancy.............<http://www.hidecs.co.uk> Mob: +44 (0)7811-639972 Tel: +44 (0)1392-426688 Going Forth Safely ..... EBA. www.electric-boat-association.org.uk.. ******************************************************************** _______________________________________________ The System Safety Mailing List systemsafety_at_xxxxxxReceived on Wed Mar 02 2016 - 13:18:24 CET
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