[SystemSafety] Software Safety Assessment

[Uma Ferrell]

1.       I agree with the previous answers on the obligatory nature of
application of specific standards per regulatory guidance or stake
holder preference or contract.

2.       One would need to ask the question, of the difference between
the standard and its update - are there new items introduced in the
updated standard that would invalidate assignment of SIL?  If you do not
now follow and apply knowledge uncovered in the latest standard, is one
really fielding an appropriately safe system?

3.       Checklists should be tailored to the tools, techniques,
language, safety measures etc - checklists are meant to be a gate to
check if the implementers followed specific techniques and avoided
problematic ones that are particular and peculiar to that system which
would avoid/lessen latent problems.  If the new standard has uncovered
some new hazard that needs attention, then there may be need for a delta
review or a delta test or use of a static verification tool to make sure
that known hazards are addressed.

On one hand we have a question of legal obligation and on the other a
professional obligation.


Best,

Uma   

 

From: systemsafety-bounces at lists.techfak.uni-bielefeld.de
[mailto:systemsafety-bounces at lists.techfak.uni-bielefeld.de] On Behalf
Of Carl Sandom
Sent: Wednesday, July 08, 2015 5:54 AM
To: systemsafety at lists.techfak.uni-bielefeld.de
Subject: [SystemSafety] Software Safety Assessment

 

Consider the following scenario:

 

In 2004 Project A software was assessed against a safety standard (let's
call it Standard X). Standard X had a very prescriptive list of software
safety requirements and a simple checklist was used for assessing SIL1
compliance. 

 

In 2014, Project B began to integrate significant new functionality into
Project A. Standard X, which was by 2014 an obsolete standard, was used
to assess the significantly smaller software baseline of Project B.
Under modern scrutiny, the simple Standard X checklist used for Project
A in 2004 was not as explicit as it could have been and it was decided
to use an improved checklist for Project B. 

 

A couple of important questions can be raised with this scenario:

 

1. Is it acceptable to use an obsolete safety standard to assess
software?

 

2. Is the SIL1 claim for 10 year old Project A invalid because the
checklist could have been better?

 

3. If Project B used the old checklist from Project A would that be
adequate?

 

I've been having some interesting discussions with the Project Managers
involved, any thoughts?

 

Regards

Carl

_________________________________

Dr. Carl Sandom CErgHF CEng PhD

Director

iSys Integrity Ltd.

+44 7967 672560

carl at isys-integrity.com

www.isys-integrity.com

_________________________________

 

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