Automatic Generation of Graceful Programs
Traditionally, (nonmasking and masking) fault tolerance
has focused on ensuring that after the occurrence of
faults, the program recovers to states from where it continues
to satisfy its original specification. However, a problem with
this limited notion is that, in some cases, it may be impossible
to recover to states from where the entire original specification
is satisfied. For this reason, one can consider a fault-tolerant
graceful-degradation program that ensures that upon the
occurrence of faults, the program recovers to states from
where a (given) subset of its specification is satisfied. Typically,
the subset of specification satisfied thus would be the critical
requirements.
In this paper, we focus on automatically revising a given
program to obtain a corresponding graceful program, i.e.,
a program that satisfies a weaker specification. Specifically,
this step involves adding new behaviors that satisfy the given
subset of specification. Moreover, it ensures that during this
process, it does not remove any behavior from the original
program. With this motivation, in this paper, we focus on
automatic derivation of the graceful program, i.e., a program
that contains all behaviors of the original program and some
new behaviors that satisfy the weaker conditions. We note
that this aspect differentiates this work from previous work
on controller synthesis as well as automated addition of fault tolerance
in that this work requires that no new behaviors are
added in the absence of faults.
Paper:
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