Use surprising results to discover a different problem

Suppose the first model gave A an unqualified favorable result because it represented the round but omitted other assignments. Ask what must be true for that result to hold. Inspecting the rota now reveals that the same attendant must be at the security desk from 10:00 to 10:15, while the modeled correction requires leaving it for a round from 10:00 to 10:10. No substitute is assigned. These stipulated facts defeat the simultaneous arrangement.

The discovery changes the model and the problem. Add the required desk coverage and its relation to the attendant’s available work; then revise A’s count availability for this interval. The earlier claim that a completed, timely inspection can supply a count still holds. B’s separate technical hypothesis also survives. What fails is the premise that A’s work can coexist with the retained service obligations.

The next question is now: how can current guidance and desk coverage both be obtained in this interval? Another discussion asking the attendant to agree with the plan supplies no missing time or replacement. The manager who controls assignments must examine a different allocation or contributor. OCE.11 develops that coordination when change work competes with continuing service.

Work backward from the joint requirement. Current guidance needs an adequate count and publication; desk coverage needs a person at the desk. One candidate is a separately allocated competent checker while the attendant remains at the desk. Test it forward: can that person obtain the count, update the display in time and do so without abandoning another necessary assignment? Naming a replacement is not that test. Until these conditions are established, the candidate is a question for the manager, not an available solution.

For a bounded continuation, suppose the manager assigns a competent relief worker for this interval, verifies that no other required assignment overlaps, and provides the permitted access and existing checking procedure. In the stipulated trial the relief worker obtains and publishes a count meeting the agreed freshness and accuracy conditions, while the attendant remains at the desk. Both required contributions are supplied in this interval. The added staffing cost belongs in A’s cost account. If relief is available only today, retain today’s result and reopen the staffing question before promising tomorrow’s service; the earlier investment question remains open.

A different candidate might change the update interval or the information promised to drivers. That changes the service requirement, so return to whether the altered guidance remains useful and acceptable. Do not weaken the criterion silently to make the diagram succeed. An incompatible candidate can be rejected without proving that all possible arrangements fail; an unsupported candidate stays conditional.

Keep the unsuccessful combination and the reason it failed so that the next attempt does not repeat it. In a formal backward analysis, ask which supported conditions and judgements produce the incompatibility. A solver’s failure can concern its encoding, restrictions or current assumptions; it is not a proof that the real organization has no remedy.