OPS.10.2:5.2 - A failed short-task priority is not an impossible deadline

Two jobs are ready at zero. U needs three hours of one specialist followed by seven hours of unattended equipment work. V needs two hours of that specialist followed by one unattended hour. The equipment is different for the two jobs, all resources are continuously available, and both results are required by hour ten.

Doing the shorter specialist task first gives V at 0-2, its equipment at 2-3, U at 2-5 and its equipment at 5-12. That plan misses the deadline.

Doing U first gives specialist intervals U at 0-3 and V at 3-5. U’s equipment runs at 3-10 and V’s at 5-6. Both dates are met. U’s own required chain takes ten hours, so the plan also attains the lower bound for the last completion.

In the first plan, the chosen resource relation V-before-U makes V part of the sequence controlling the final finish. In the second plan, V can finish well before U. That criticality was a consequence of the selected order. Five hours of specialist demand alone revealed neither the successful order nor the ten-hour completion.