Re: [SystemSafety] Agile methods

From: Les Chambers < >
Date: Sat, 31 Aug 2013 11:53:29 +1000

Hi Rene

As you may have sensed by now, mentioning agile development in a room full of functional safety engineers introduces a stench that makes you want a look around and ask who ... It's lucky we're not crowded into a lift/elevator. Having said that, in my own practical experience, elements of the agile philosophy can be applied to functional safety. While a hazard analysis is done at the beginning of a project and functional safety requirements derived from it, these requirements are never complete or static. This is why most standards require the generation and maintenance of a hazard log throughout a project. Hazards arise from the operational environment but can also be introduced by design approaches. Also there are always those oops moments when, on thinking through a problem in great detail, you gain insights that were not possible at the beginning of the project. Then there is always the guy with the knowledge that wasn't invited to the hazard analysis sessions and turns up with whole new take on safety including hard knowledge of past safety incidents that no one knew about.

The job of a functional safety engineer is to sit in on design reviews and highlight and document these hazards together with the agreed corrective action. In a practical sense the response to a hazard should be some kind of safety requirement that must be validated in the end product and verified in the design as it progresses. As one who has had the job of running a hazard log and closing it out at the end of the project I would like to see a more agile approach to implementing some of these in-process generated requirements. This is where agile comes in. The fundamental principle of agile is incremental generation of requirements in close cooperation with the customer and regular demonstration of progress in implementing those requirements that allows a customer to give feedback. Too many projects I have been associated with have left implementing in-process generated requirements far too long to the point where it's almost too late and very expensive to do the necessary work, hence the need for more agility and a faster turnaround on implementing requirements in the design.

In summary, using agile as the core methodology for a safety critical system build is just not practical but using agile ideas in aspects of such a project can be beneficial. In other words I'm advocating a mash up which inevitably happens in the real world.

A note of caution though: if you are working with an organisation that insists on using 100% agile principles in a safety critical system build its highly likely they have no experience in that field and are dangerous people. Run!!



From: systemsafety-bounces_at_xxxxxx [mailto:systemsafety-bounces_at_xxxxxx René Senden
Sent: Saturday, August 31, 2013 3:30 AM
To: 'Nancy Leveson'
Cc: systemsafety_at_xxxxxx Subject: Re: [SystemSafety] Agile methods  

I appreciate your input, however, my question addresses a specific situation that some of you may have encountered in practice…

It is such practical experience I am interested in…

Let me rephrase… I was not very clear/accurate in describing my query…

Have you encountered a situation, in industrial practice, in which an organization developing software following an agile methodology

has to comply with a safety standard which has specific requirements on the software development process? A typical example of

such safety standard, with respect to its requirements on the sw-dev, would be IEC-61508 Part 3 or DO-178…  


From: Nancy Leveson [mailto:leveson.nancy8_at_xxxxxx Sent: vrijdag 30 augustus 2013 19:14
To: René Senden
Cc: systemsafety_at_xxxxxx Subject: Re: [SystemSafety] Agile methods  

Definitions always differ among the users of terms. But if the Agile methods being considered do not start with a complete and thorough specification of all the system/software safety requirements before anything else, then the system resulting system/software design will almost surely be less safe than one that does. Whether it coincides with other standards (most of which are very deficient with respect to safety) is not really important, is it?  


On Fri, Aug 30, 2013 at 1:02 PM, René Senden <rene.senden_at_xxxxxx

Dear all,

Do any of you have practical experience with reconciling established agile software development with software safety requirements (e.g. IEC-61508 or DO-178..) ?

Best regards,

The System Safety Mailing List
Prof. Nancy Leveson
Aeronautics and Astronautics and Engineering Systems
MIT, Room 33-334
77 Massachusetts Ave.
Cambridge, MA 02142

Telephone: 617-258-0505
Email: leveson_at_xxxxxx

The System Safety Mailing List systemsafety_at_xxxxxx
Received on Tue Sep 03 2013 - 09:34:30 CEST

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