C.29.3:2 - Problem

An abstract operation can be well defined while its proposed execution changes the question. The integer 63,662 can be the right calculated command and be delivered as -1,874 by an overflowing signed field. A circuit can correctly average two voltages while its user reads that average as their sum. Two attendants can each follow the same capacity rule while admitting twice the intended number of visitors through duplicated stocks.

The failure can occur before execution, during intermediate actions or when the result is interpreted. More arithmetic at the middle of the calculation leaves those failures in place. A successful trace of one input can also leave another required input outside the representable range, or omit an interleaving that breaks a shared-state assumption.

A practitioner needs to construct the correspondences, establish the property needed by the receiving use and locate which part to change when the interpreted execution fails to supply that property. The useful comparison can concern a value, a bound, a probability distribution or a property maintained throughout an interaction.