[SystemSafety] COTS display certification

[Peter Bernard Ladkin]

On 2016-07-27 10:02 , jean-louis Boulanger wrote:
> It's not mistake ...

Yes, it is. See below.

> IEC 61508 said some things ... CENELEC said another think and DO xxxx a different thing
> in my message I said that I work in railway ...

I have dealt with IEC 61508 already.

The notion of SIL is not present in RTCA/EUROCAE avionics safety standards. The notion is DAL and is
very different. DAL is a measure of the criticality of the element to which it is assigned.

The notion of SIL in the CENELEC railway standard EN 50128 is explicitly as follows:

[begin quote]

3.1.29
 safety function
 a function that implements a part or whole of a safety requirement

3.1.30
 safety-related software
 software which performs safety functions

.....
3.1.37
 software safety integrity level
 classification number which determines the techniques and measures that have to be applied to
 software

 NOTE Safety-related software has been classified into five safety integrity levels, where 0 is the
 lowest and 4 the highest.
......

3.1.39
 system safety integrity level
 classification number which indicates the required degree of confidence that an integrated system
 comprising hardware and software will meet its specified safety requirements

[end quote]

The notion of "safety requirement" is not defined in EN 50128. However, just as in IEC 61508, safety
functions are those things which implement a safety requirement, safety-related SW is software which
performs a safety function and SW SIL is a number between 0 and 4 which software which implements a
safety function is assigned.

What you said is:

On 2016-07-26 18:33 , jean-louis Boulanger wrote:
> In new OCC system, some vital information are displayed on control screen and this informations is
> SIL x or DAL x.

I said this is a category mistake, and that is correct. There is in EN 50128 no notion that
information displayed on a screen acquires a SIL. SILs are assigned to SW which implements safety
functions.

PBL

Prof. Peter Bernard Ladkin, Bielefeld, Germany
MoreInCommon
Je suis Charlie
Tel+msg +49 (0)521 880 7319  www.rvs-bi.de





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