Niwot Ridge Resources

A Source of Information for Mission Critical Systems, Management Processes, and Strategies

High Integrity Systems

There has been much discussion about the deployment of Light Weight or Agile development methods in a variety of software domains. Before one gets too excited about this trend some background on the design and development of High Integrity Systems would allow an informed decision to be made.

IEC 61508 is a standard for high integrity systems. Draft IEC 61508(2) requires that a target safety integrity level (SIL) be assigned for any new or retrofitted safety instrumented systems (SIS). The SIS consists of the instrumentation or controls that are installed for the purpose of mitigating the hazard or bringing the process to a safe state in the event of a process upset. A SIS is used for any process in which the process hazards analysis (PHA) has determined that the mechanical integrity of the process equipment, the process control, and other protective equipment are insufficient to mitigate the potential hazard.

SEMI 2 safety standards for software based systems

Triplex ICS product.

Triconex product - I was the manager of software development for this firm.

Nancy Leveson's System and Software Safety Research Project.

Kishor Trevedi's Software Rejuvenation site.

Links to High Integrity Systems in the process industry

Software Reliability

DACS (Data and Analysis Center for Software) Software Reliability

Reliability Analysis Center

Centre for Software Reliability

Failure Mode Effects Analysis is an easy to use and yet powerful pro-active engineering quality method that helps identify and counter weak points in the early conception phase of products and processes. The structured approach makes it easy to use and even for non-specialist a valuable tool. The benefits obtained encompass by large the investments in time and resources to execute the analysis.

The ISO/TS 16949 is part of FMEA guidelines as are other ISO and Quality Standards.

There are several people that have resources for reliability, these include:

Normal Fenton is Professor of Computing at Queen Mary and Westfield College (London University) and is also Managing Director of Agena, a company that specializes in risk management for critical systems.

Dick Hamlet Professor, Department of Computer Science, Portland State University.

Jonathan Bowen is a Professor of Computing, at the Centre for Applied Formal Methods, SCISM, South Bank University, London.

Victor Basili is a professor at the University of Maryland. Dr. Basili is a noted advocate and practitioner of quantitative methods in software engineering.

Safety Critical Systems

Safety Critical Systems are a domain on interest as well as profession. The discussions on the XP and OTUG forums sometimes present opportunities for the participants to make sweeping statements about things they know little about, when it comes to fault tolerant safety critical systems. Here are some resource links for those interested:

Statistical System Testing based on the Results at Sizewell B and On-Going Research

Triconex Corporation for whom I worked and designed the fault tolerant embedded diagnostics as well as managing the development group.

Centre for Software Reliability

Peter Neumann is a Principal Scientist at SRI. From his site access to many other safety Critical Systems site is available.

Information Survivability for Critical Infrastructure Protection

Denver ATC, Longmont

National Transportation Safety Board


European Workshop on Industrial Computer Systems has a links page to safety critical systems, standards and guidelines.

WWW Virtual Library for Safety Critical Systems

Advances in Safety Critical Systems


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