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 |
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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.
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| Ariane 5 |
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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.
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| Barclays Bank |
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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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