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E. Shokri, H. Hecht, Matching Software Fault Tolerance and Application Needs,
Second High-Assurance Systems Engineering WorkShop HASE 98, November 1998
The designation of fault tolerant software has been used for techniques ranging
from roll-back and retry to N-version programming, from data mirroring to functional
redundancy. If the term is to be meaningful, qualifying definitions are required.
This paper attempts to provide these by analyzing the capabilities of representative
software fault tolerance techniques described in prior literature and matching these
with the needs of representative environments in which fault tolerance may be applied.
This paper suggests five categories for comparison of application needs and fault-tolerance
capabilities: accuracy, deadline, state preservation, coverage, and economy of resources.
It then shows how representative needs and capabilities can be characterized in
identical terms by these categories. Algorithms are developed for either ranking
(ordering) the importance of categories or assigning weighting factors to them.
The algorithms suggest partially-suitable matches where there is no complete match
between the application needs and the capabilities of fault-tolerance techniques.
Examples of the selection technique are presented.
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