|
H. Hecht, D. Wallace, "Error Classification and Analysis for High Integrity
Software", The 1996 American Nuclear Society International Topical Meeting on Nuclear
Plant Instrumentation, Control and Human- Machine Technology, Pennsylvania State
University, USA, May, 1996
High integrity software includes that in aircraft flight control, nuclear reactor
safety systems, and portions of the ground based air traffic control. One of the
best known specifications for such software establishes a maximum tolerable failure
rates for the most severe modes of 10-10/flight-hr.[ FAA88]. Demonstration of the
attainment of such low failure rates is not possible by the established methods
of software reliability estimation, e. .g, [MUSA87]. Indeed, a large fraction of
the development cost of high integrity systems must be devoted to the assessment
of their dependability through software quality assurance, inspection and test.
Yet most serious students of the field agree that none of the assessment methods
and tools currently employed provides an estimate that has a high correlation with
the achieved dependability for the required high reliability levels. Because we
do not know what and how much the individual steps of the assessment contribute
to assurance of freedom from failure (and the validity of the estimate), there is
a distinct possibility that the efficiency of the effort could be much improved.
Similar uncertainty exists regarding the value of development methodologies and
tools for the attainment of extremely high software reliability. The total development
and assessment cost for high integrity systems is so large that even a small reduction
of the effort by replacement of ineffective with more effective procedures will
result in large economic benefits.
Click to Download
|
|
