A systematic approach to software safety integrity levelsPeter

Note: Most SVRC technical reports are available via anonymous ftp, from svrc.it.uq.edu.au in the directory /pub/techreports. Individual abstracts and compressed postscript les are available from Abstract International Standards for safety-critical software typically use notions of Safety Integrity Levels (SILs) which in our experience are dif-cult to apply and which lack credible assessment criteria. This paper proposes risk modelling as a basis for allocation of SILs to software and illustrates its use. It also proposes software-directed evaluation criteria for SILs, to assess what level of integrity is actually achieved. We contend that the approach leads to more credible results, and more cost-eeective ways of delivering software safety assurance .