[SystemSafety] Fwd: Rethinking Safety and Security/11 PCB Layout Myths

SPRIGGS, John J John.SPRIGGS at nats.co.uk
Thu Dec 8 09:58:33 CET 2016


For RTCA/DO-178 and ED-12 the software level is associated with the severity of the risk, other schemes use levels based on risk 'likelihood' and are thus orthogonal.

John

-----Original Message-----
From: systemsafety [mailto:systemsafety-bounces at lists.techfak.uni-bielefeld.de] On Behalf Of David MENTRÉ
Sent: 08 December 2016 08:20
To: systemsafety at lists.techfak.uni-bielefeld.de
Subject: Re: [SystemSafety] Fwd: Rethinking Safety and Security/11 PCB Layout Myths

Hello,

On 12/08/2016 06:35 AM, Peter Bernard Ladkin wrote:
> Wong makes the common mistake of formulating equivalence between 
> "levels", here the Design Assurance Levels (DAL) of avionics with the Automotive Safety Integrity Levels (ASILs) of ISO 26262.

I would make the same mistake.

> DALs are criticality levels. How critical something is to the 
> operation of the system, and therefore what level of assurance to which it should be subject.
>
> A SIL is a reliability requirement on a safety function. A safety 
> function is something whose action reduces an unacceptable risk of a 
> specific hazard to an acceptable risk. It operates as designed only if the reliability requirement set by the SIL is fulfilled.
>
> In principle, all safety functions have the same criticality: they are 
> all critical, period. So, one criticality level, rather than the five of ED-12C.

[disclaimer: I never looked at ED-12C / DO-178C text.]

So all SIL A to D of ISO 26262 would correspond to one DAL of EC-12C? 
Which one? DAL A?

If this the case, why make the difference between several "sub-DAL-As" 
in ISO 26262?

 From my software engineering point of view, ISO 26262 SILs and EC-12C/DO-128C DALs are the amount of work to reach a certain level of quality of the software, and in that sense are similar.

Best regards,
D. Mentré
_______________________________________________
The System Safety Mailing List
systemsafety at TechFak.Uni-Bielefeld.DE

***************************************************************************
If you are not the intended recipient, please notify our Help Desk at Email information.solutions at nats.co.uk
immediately. You should not copy or use this email or attachment(s) for any purpose nor disclose
their contents to any other person.

NATS computer systems may be monitored and communications carried on them recorded, to 
secure the effective operation of the system.

Please note that neither NATS nor the sender accepts any responsibility for viruses or any losses
caused as a result of viruses and it is your responsibility to scan or otherwise check this email
and any attachments.

NATS means NATS (En Route) plc (company number: 4129273), NATS (Services) Ltd 
(company number 4129270), NATSNAV Ltd (company number: 4164590) 
or NATS Ltd (company number 3155567) or NATS Holdings Ltd (company number 4138218). 
All companies are registered in England and their registered office is at 4000 Parkway, 
Whiteley, Fareham, Hampshire, PO15 7FL.

***************************************************************************



More information about the systemsafety mailing list