[SystemSafety] Modelling and coding guidelines: "Unambiguous Graphical Representation"

[GRAZEBROOK, Alvery N]

Thierry,

In response to your note, I think you are conflating 2 issues:
 - re-use of actual components such as nuts and bolts, or power transistors, which come off the same production line and the whole thing comes "as packaged"
 - design re-use, where you copy/paste design information and then put it in a new "context" on a new production line.

There are some similarities, but in the first case you are trying to gain advantage by proven characteristics actually being met, whereas in the second case you are trying to gain advantage by accepting the design process carried out by the previous group of designers. These are very different things. 

Cheers,
	Alvery

** any opinions here are my own, not necessarily those of my employer.

From: systemsafety [mailto:systemsafety-bounces at lists.techfak.uni-bielefeld.de] On Behalf Of Coq, Thierry
...

The argument about trusting proven in use components has been completely disproved by the Ariane 501 flight and its consequences.
A proven-in-use component in one environment may be replete with defects that may emerge in another environment.
It also has disproved most ways of thinking probabilities of failure for software-dependent systems.

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