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H. Hecht, M. Hecht, "Dependability Assessment for Decentralized Systems",
Proc. Second International Symposium on Autonomous Decentralized Systems, Phoenix,
AZ, April, 1995
Conventional dependability measures, such as reliability or availability, assume
that the equipment characterized by the measure is either operational or has failed.
This dichotomy does not hold for decentralized or distributed systems because these
can operate in modes in which partial or degraded service is furnished. Whether
a specific degraded mode should be counted as "operational" or "failed" is a subjective
decision, but this decision can make a large difference in the dependability assessment.
Examples show that this will affect not only numerical reporting, but also the selection
of reliability improvements. A weighted averaging of the dependability measures
obtained under various failure criteria is seen to be a workable method for reliability
assessment that provides much more stable measures than can be obtained by selection
of a single failure criterion.
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