Xiao Liu PhD Thesis.pdf - Faculty of Information and Communication ...

7.1.2 Problem Analysis
In the existing work on temporal verification, checkpoint selection is not regarded as
an independent task since they normally adopt the philosophy that temporal
violation handling should be conducted whenever a temporal violation is detected,
i.e. temporal violation handling point selection is the same as checkpoint selection.
Accordingly, no matter whether it is a major time deficit of 35 minutes or a minor
time deficit of 3 minutes as described in the motivating example in Section 1.2, a
temporal violation handling is triggered. However, in the real world, it is normally
unnecessary to trigger temporal violation handling for a minor time deficit since
there is a high probability that it will be automatically compensated for by the time
redundancy of the subsequent activities. Therefore, as a matter of fact, a checkpoint
is not necessarily a temporal violation handling point.
The challenging issue for temporal violation handling point selection is “how to
select the key checkpoints where temporal violation handling is necessary”. To
address such an issue, we need to solve the following two major problems.
1) How to measure temporal violations in a quantitative fashion
In order to reduce the temporal violation handling cost, we need to detect those
“minor” temporal violations with relatively small time deficit. Therefore, it is
important that we are able to measure temporal violations in a quantitative fashion.
However, the existing temporal consistency models utilise static time attributes such
as the maximum and mean durations to define coarse-grained qualitative expressions
such as the violation of strong consistency or weak consistency to measure the
occurred temporal violations [20, 22]. To facilitate the statistical analysis of the time
deficit and the time redundancy, it is better to model activity durations with dynamic
variables (following a probability distribution) instead of static time attributes,
especially in dynamic system environments [49, 54]. Therefore, a temporal
consistency model which can facilitate the quantitative measurement of temporal
violations is required.
2) How to decide whether a checkpoint needs to be selected as a temporal
violation handling point or not
Reduce the temporal violation handling cost is to omit those checkpoints where
minor time deficits have a high probability of being compensated for by the
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