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Society's dependence on computer-based systems

Society's dependence on computer-based systems continues to increase. The systems themselves - embracing humans, computers and engineered systems - become ever more complex as they feed an insatiable appetite for new and extended functionality. Furthermore, these trends coincide with pressure for systems to be brought to market faster and at lower (and more predictable) cost. Achieving sufficient dependability in these systems, and demonstrating this achievement in a rigorous and convincing manner, is of crucial importance to the fabric of the modern Information Society.

Classical case studies


Therac-25 accidents involving massive radiation overdoses to patients occurred between 1985 and 1987. The machine was recalled in 1987 for extensive design changes, including hardware safeguards against software errors.

An Investigation of the Therac-25 Accidents by Nancy Leveson, University of Washington and Clark S. Turner, University of California, Irvine is available.

Ariane 5  
  Ariane 5

On 4 June 1996, the maiden flight of the Ariane 5 launcher ended in a failure. Only about 40 seconds after initiation of the flight sequence, at an altitude of about 3700 m, the launcher veered off its flight path, broke up and exploded. The origin of the failure was rapidly narrowed down to the flight control system and more particularly to the Inertial Reference Systems, which obviously ceased to function almost simultaneously. The extensive reviews and tests carried out during the Ariane 5 Development Programme did not include adequate analysis and testing of the inertial reference system or of the complete flight control system, which could have detected the potential failure.

The Report by the Inquiry Board is available.


Barclays Bank  

On 31 July 2000, a security breach apparently caused by a software upgrade forced London-based Barclays Bank to temporarily shut down its online banking service after four customers reported that they were able to view summaries of accounts belonging to other people.

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