software reliability

Motor Industry Software Reliability Association

The Motor Industry Software Reliability Association (MISRA), is a collaboration between vehicle manufacturers, component suppliers and engineering consultancies which seeks to promote best practice in developing safety-related electronic systems in road vehicles and other embedded systems. To this end MISRA publishes documents that provide accessible information for engineers and management, and holds events to permit the exchange of experiences between practitioners.

The MISRA mission statement is: "To provide assistance to the automotive industry in the application and creation within vehicle systems of safe and reliable software."

What is MISRA?

Due to the growth in the electronics content of vehicles, including software, MISRA project started in 1990 to provide practical “how to” guidance for developing safe and reliable vehicle electronic systems.

MISRA published its first Guidelines in November 1994. This was the results of a collabration of the following organisations (names are correct as of 1994):

The MISRA consortium was formed in response to the UK Safety Critical Systems Research Programme, supported by the Department of Trade and Industry and the Engineering and Physical Sciences Research Council (EPSRC).

Current MISRA Members

  • Controlling Members of MISRA
    • AB Automotive Electronics Ltd
    • Bentley Motor Cars
    • Ford Motor Company Ltd
    • Jaguar Cars
    • Lotus Engineering
    • MIRA (also Project Manager)
    • Ricardo plc
    • TRW
    • University of Leeds
    • Visteon Engineering Services Ltd

What does MISRA do?

MISRA aims to

  • Promote best practice in automotive safety-related systems engineering
  • Develop guidance in specific technical areas where there is a perceived gap in existing guidance e.g.
    • C language
    • C++ language
    • Model based development and autocode
    • Safety analysis

MISRA does not

  • Operate certification schemes
  • Promote or endorse specific products

MISRA Guidelines

Development Guidelines for Vehicle Based Software published in 1994. Also available as ISO/TR 15497

Key features

  • Based on principles of IEC 61508
  • “Goal based”, not prescriptive
  • Use of safety integrity level (SIL) as measure of target risk reduction
  • Development rigor related to SIL

MISRA C

  • First published in 1998; updated in 2004
  • Perhaps the best-known MISRA publication
  • Created for specific requirement of 1994 Guidelines “Subset of a standardized structured programming language”
  • Avoid or control use of well-known (and less well-known) issues in the C language
  • C’s arithmetic model
  • Widely adopted
  • Ongoing work

MISRA SRfP

SRfP -> Software Readiness for Production

Software seen as cheap and easy to modify

  • Add new features
  • Solve hardware-related issues

How to measure impact of software “readiness” on production release?

Process for physical components – PPAP

Why not for software?

MISRA SRfP provides “completeness” metric for software

MISRA Safety Analysis

MISRA 1994 requirements

  • Preliminary safety analysis
  • Detailed safety analysis

Neither explained in detail

Need for more explicit mapping to IEC 61508

Forthcoming ISO 26262

  • New safety management processes?

MISRA SA provides guidance on all these areas

MISRA C++

Growing use of C++ in critical applications

  • Less evident in automotive … so far

MISRA C++ similar in concept to MISRA C

  • Identify known issues in the language
  • Provide rules to control or avoid use of unpredictable features
  • Official launch 5 June 2008

MISRA Autocode

Model based development and automated code generation now “state of the art” in automotive Model may be viewed as the “language” Similar “language” issues to e.g. C

  • Unpredictable features
  • Need for a subset e.g. IEC 61508
  • Stylistic issues

New series of documents

Current Activities

Development continuing on “languages” issues e.g. MISRA C3, further Autocode documents

Started to examine common “language” issues

Further process measures

Systems engineering

ISO 26262 adoption

External links

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