This layer presents questions that focus on the duration and timing of an action abstract- ing other details about the action. The questions challenge the start-time, end-time and duration of the action with different variations. All the questions in this layer refer to the problem formulation. Any change in the duration or start-time of the actions implies a plan revision or plan check task. This questions then provide pointers in which a check task is needed.
CQAT-01. Is the action possible with the specified duration?
This question challenges the possibility of the action related to its duration. A conflict in the action duration specification between agents can lead to discard the action. An agent ag has reason to believe an action is not possible with the specified duration if in its local specification the action duration has a different value. Example: Consider a situation where agent P KF presents action moveEscorted(N GO,6,8) with duration 2 (see Table ??) in a plan. Agent N GO can question the action duration since its local definition of the action moveEscorted() the action duration has value 3 (see Tables A.4 and??).
The action moveEscorted(N GO,6,8)is not possible with duration 3.
CQAT-02. Can the action duration be less?
This question aims to change the duration of the action by reducing the duration of it. An agent ag has reason to believe the duration of an action can be less iff: (1) the action has a range different to 0, and (2) the proposed new duration is at least the original duration minus the range, and (3) the change does not prevent the goal to be achieved. An agent knows that reducing the duration of the action does not prevent the goal to be achieved by performing a plan check (cf. Section 3.1, the agent has a plan checker that verifies the plan achieves the goal). Example: Consider planP LF where agentN GOpropose actionprepareResources() with duration 2 at timet4. Agent P KF can suggest to reduce the duration of the action (since the range of the action allows it) to a duration of 1 and start action escort(P KF, N GO,7,8, d(4)) at t4 and save time.
CQAT-03. Can the action duration be longer?
This question aims to change the duration of the action by extending the duration of it. An agent ag has reason to believe the duration of action Ac can increase iff (1) the action has a range different to 0 and (2) the proposed new duration is at least the original duration plus the range and (3) the change does not prevent the goal to be achieved.
Consider planP LF where agentN GOpropose actionescort(P KF, N GO,6,7, d(4)) with duration 4 at timet0. Agent P KF can suggest to increase the duration of the action (since the range of the action allows it) to a duration of 5 and start action escort(P KF, N GO,7,8, d(4)) at t4. Note that this change affects the execution of actionmoveEscorted() and thus the planner may have to reschedule the actions of N GO.
Can the action escort(P KF, N GO,7,8, d(4)) have duration 5?.
CQAT-04. Is the action Ac possible at the specified start time t?
The possibility of an action at a specific time can be challenged with this ques- tion. The action may be possible with the specified duration but not at the specified start time t. An agent ag has reason to believe the action Ac is not pos- sible at timetiff according to the agentagthe preconditionpwill not hold at timet. Example: Consider N GO’s plan P LF (see Table A.19) and the action moveEscorted(N GO,8,14, d(3)) at time t8. The action cannot be performed at time t8 since the precondition groundF orce(vigilant) will not be met since action escort needs to start before.
CQAT-05. Can the action Ac start earlier?
This question aims to change the start time of the action without preventing the goal to be achieved. An agentag has reason to believe an actionAcstarting at time t can start earlier iff either by (1) extending the action duration within the range or (2) moving the action to a earlier start timeti and the goal is still achieved. Example: Consider action move(P KF,4,5, d(3)) at t4 in plan P LB (see Ta- ble A.17). The action can be performed earlier at timet3 without affecting the plan outcome.
Is it possible to change the start time of action move(P KF,4,5, d(3)) to t5?. The action can also can be performed att3with duration 5 (move(P KF,4,5, d(5))) since the range allows it. As explained at the beginning of this section the answer and creation of this question depends on a plan check.
CQAT-06. Can the action Ac start later?
This question aims to change the start time of the action to a later time without affecting the plan. An agentag has reason to believe an actionAccan start later iff either by (1) extending the action duration within the action range or (2) changing the action to a later start time ti does not prevent the goal to be achieved.
Example: Consider actionmove(P KF,4,5, d(3)) att4in planP LB(see Table A.17), the action can be performed later at time t5 without affecting the plan outcome. Is it possible to change the start time of action move(P KF,4,5, d(3)) to t5?.