Safety when expressed quantitatively as the probability of a loss over some unit of exposure, is in effect a proportional rate. This is useful as we can compare the performance of different systems or operations when one has of operating hours, and potentially lots of accidents while another has only a few operating hours and therefore fewer accidents. Continue Reading…
Archives For Risk
What is risk, how dow we categorise it and deal with it.
I’ll give you a hint it’s not pretty
Current Australian rail and workplace safety legislation requires that safety risks be either eliminated, or if that’s not possible be reduced, ‘so far as is reasonably practical’. The intent is to ensure that all reasonable practicable precautions are in place, not to achieve some target level of risk.
There are two elements to what is ‘reasonably practicable’. A duty-holder must first consider what can be done – that is, what is possible in the circumstances for ensuring health and safety. They must then consider whether it is reasonable, in the circumstances to do all that is possible. This means that what can be done should be done unless it is reasonable in the circumstances for the duty-holder to do something less.
This is a real and intractable problem for standards that determine the degree of effort applied to treat a hazard using an initial assessment of risk (1). Nor can the legislation be put aside through appeals to such formalisms as the ALARP principle, or the invocation of a standard such as AS 61508 (2). In essence if it is practical to do something, regardless of the degree of risk, then something should be done. Continue Reading…
A short (and possibly evil) treatise on SILs from our guest blogger
May I introduce myself? The name’s Screwtape, some of you might have heard of me from that short and nasty book by C.S. Lewis. All lies of course, and I would know, about lies that is… baboom tish! Anyway the world has moved on and I’m sure that you’d be completely unsurprised to hear that I’ve branched out into software consulting now. I do find the software industry one that is oh so over-ripe for the plucking of immortal souls, ah but I digress. Your good host has asked me here today to render a few words on the question of risk based safety integrity levels and how to turn such pesky ideals, akin in many ways to those other notions of christian virtue, to your own ends. Continue Reading…
Practical risk management, or why I love living in Australia
We’re into the ninth day of closed beaches here with two large great whites spotted ‘patrolling our shores’, whatever that means. Of course in Australia closed doesn’t actually mean the beaches are padlocked, not yet anyway. We just put a sign up and people can make their own minds up as to whether they wish to run the risk of being bitten. In my books a sensible approach to the issue, one that balances societal responsibility with personal freedom. I mean it’s not like they’re as dangerous as bicycles Continue Reading…
I was cleaning out my (metaphorical) sock drawer and came across this rough guide to the workings of the Australian Defence standard on software safety DEF(AUST) 5679. The guide was written around 2006 for Issue 1 of the standard, although many of the issues it discussed persisted into Issue 2, which hit the streets in 2008.
DEF (AUST) 5679 is an interesting standard, one can see that the authors, Tony Cant amongst them, put a lot of thought into the methodology behind the standard, unfortunately it’s suffered from a failure to achieve large scale adoption and usage.
So here’s my thoughts at the time on how to actually use the standard to best advantage, I also threw in some concepts on how to deal with xOTS components within the DEF (AUST) 5679 framework.
Or how do we measure the unknown?
The problem is that as our understanding and control of known risks increases, the remaining risk in any system become increasingly dominated by the ‘unknown‘. The higher the integrity of our systems the more uncertainty we have over the unknown and unknowable residual risk. What we need is a way to measure, express and reason about such deep uncertainty, and I don’t mean tools like Pascalian calculus or Bayesian prior belief structures, but a way to measure and judge ontological uncertainty.
Even if we can’t measure ontological uncertainty directly perhaps there are indirect measures? Perhaps there’s a way to infer something from the platonic shadow that such uncertainty casts on the wall, so to speak. Nassim Taleb would say no, the unknowability of such events is the central thesis of his Ludic Fallacy after all. But I still think it’s worthwhile exploring, because while he might be right, he may also be wrong.
*With apologies to Nassim Taleb.