The Plan Ontology. OWL engineering by Aldo Gangemi.
A scheduling is a task that cannot be executed twice, since it has a temporal parameter restricted to one value, e.g. it classifies an event that is valued by a definite temporal value.
An activity related to planning. It is sequenced by 'case task', and can contain an information gathering activity.
A deliberation task is a control task that sequences deliberation states (decisions taken after a case task execution).
A case task branched to exactly 2 tasks, not executable in parallel.
A task that articulates the plan into an ordered set of tasks.
A task that joins a set a tasks after a branching.In particular, a synchronization task is aimed at waiting for the execution of all (except the optional ones) tasks that are direct successor to a concurrent or any order task.
An any order task is a branching task that defines no order in the successor tasks. Itís another way of defining a bag task, because any temporal relation can be expected between any two perdurants sequenced by the tasks that are direct successor to the any order task.
A task for parallel concurrent activities.
A concurrent task is a task branched to a set of tasks executable concurrently -the sequenced perdurants can overlap-, which means that no deliberation task is performed in order to choose among them. A concurrent task has at least one successor synchronization task, which is aimed at waiting for the execution of all -except the optional ones- tasks direct successor to the concurrent -or any order, see below- one.The axioms cannot be expressed fully in OWL-DL (no value mapping available).
A case task is a task branched to a set of tasks that are not executable concurrently. In order to choose the task to be executed, preliminary deliberation tasks should be executed. A case task sequences a decision activity (a kind of mental event involving rationality) that has a deliberation state as outcome (sequenced by a deliberation task).
A control task that directly precedes both a case task and some other task.It specializes the branching task.
A bag task is a complex task that does not include either a control task, or a successor relation among any two component tasks.The last condition cannot be stated in OWL-DL, because it needs a coreference.
A saturated plan is a plan that cannot be executed twice, since it defines spatio-temporal parameters restricted to one value, e.g. one of its tasks classifies an event that is valued by a definite temporal value in a definite space region.Of course, in the case of maximal spatio-temporal regions, a saturated plan tends to approximate an abstract plan from the execution viewpoint, but these worst cases are unavoidable when dealing with maximality.
A circumstantial plan has all components classifying named individuals from the ground ontology (e.g. only specific persons, specified resources, a finite number of time intervals and space regions, etc.).This condition cannot be formalized in FOL, since we would like to express a condition by which an instance of an circumstantial plan specifies both instances of plan components, and instances of situation elements, e.g. that 'manager' classifies a specified (named) person.
A technique to evaluate a plan execution.
A main goal can be defined as a goal that is part of a plan but not of one of its subplans. The characteristic axiom cannot be formalized in OWL-DL (it requires coreference).
An abstract plan is a plan whose roles and tasks only specify classes of entities that can be included in a plan execution. In other words, a component from an abstract plan does not classify any named entity. This condition cannot be formalized in FOL, since we would like to express a condition by which an instance of an abstract plan specifies instances of plan components, but no instances of situation elements, e.g. that 'manager' classifies some (if any) instance of person, but not a specified (named) person.
A maximal task is a complex task that has all the tasks defined in a plan as components.In OWL-DL the axiom is defined as a concept axiom over plan component task.
A task that has at least two other tasks as components.
An activity aimed at gathering information for some purpose. It is typically sequenced by case tasks for taking decisions (can be part of decision activities).
Plan executions are situations that proactively satisfy a plan (cf. definition of P-SAT above). Subplan executions are proper parts of the whole plan execution.
An action task is an elementary task that sequences non-planning activities, like: moving, exercising forces, gathering information, etc. Planning activites are mental events involving some rational event.
A control task is an elementary task that sequences a planning activity, e.g. an activity aimed at (cognitively or via simulation) anticipating other activities. Therefore, control tasks have usually at least one direct successor task (the controlled one), with the exception of ending tasks.The reification of control constructs allows to represent procedural knowledge into the same ontology including controlled action. Besides conceptual transparency and independency from a particular grounding system, a further advantage is enabling the representation of coordination tasks. For example, a manager that coordinates the execution of several related activities can be represented as a role with a responsibility (duty+right) towards some complex task.
A goal situation is a situation that satisfies a goal.Opposite to the case of subplan executions, a goal situation is not part of a plan execution.In other words, it is not true in general that any situation satisfying a part of a description, is also part of the situation that satisfies the whole description. This helps to account for the following cases: a) Execution of plans containing abort or suspension conditions (the plan would be satisfied even if the goal has not been reached, see below), b) Incidental satisfaction, like when a situation satisfies a goal without being intentionally planned (but anyway desired).
The technique by which a planning process can be carried out.
A state related to planning. It is sequenced by 'deliberation task', and is preceded by a decision activity.
A sequential task is a complex task that includes a successor relation among any two component tasks, and does not contain any control task.The first condition cannot be stated in OWL-DL, because it needs coreference.
The execution of a task (an action classified by it) can make a new situation emerge: in this case the task has a task-postcondition.
iteration interval can be used to state how much time should be taken by each iteration of the looped activity
The execution of a task (an action classified by it) can require that a situation holds: in this case the task has a task-precondition.
The relation between a plan and its main goal.
A relation between a goal and the main goal of the plan it is a subgoal of. Usable for talking of dependencies between goals.
A situation is a pre-condition of the execution of a method (and of its tasks) when it is a predecessor (however succession is interpreted, although temporal interpretation is the usual one) of that execution, and is constituted by a subset of the individuals that constitute the execution situation. For example, a surgical guideline describes how to carry out a heart transplant: its (expected) execution situation is constituted by the perdurants, endurants, and regions described by the guideline, while its pre-condition situation might be only constituted by the heart to be removed, the one to be transplanted, their anatomical and morphological environment, the physiological functions in which they participates, and some physiological values. But the devices used during the transplantation and the surgeon might (or might not) be external to the pre-condition situation. This definition does not cover the possibility of a pre-condition having constituents that are not involved in the description. This is a difficult issue. A possible solution is that such pre-conditions are actually referenced by other descriptions that -for instance- 'control' the feasibility of a procedure, or 'analyze' a set of events under an independent unity criterion. If this solution is applicable, such pre-conditions would be 'maximal' situations requiring the 'composition' of two or more related descriptions.
A subgoal (relative to a plan) is a goal that is a part of a subplan.A goal is not necessarily a part of the main goal of the plan it is a subgoal of. E.g. consider the goal: being satiated; eating food can be a subgoal of the plan that has being satiated as its main goal, but it is not a part of being satiated.See also relations: influence, disposition to.
The goal state described by the goal of a plan can be achieved by executing activities that are sequenced by some task (either elementary or complex). The relation between the goal and the task is called here 'achievable-through'.
A situation is a post-condition of the execution of a method (and of its tasks) when it is a successor (however succession is interpreted, although temporal interpretation is the usual one) of that execution, and is constituted by a subset of the individuals that constitute the execution situation. For example, a surgical guideline describes how to carry out a heart transplant: its (expected) execution situation is constituted by the perdurants, endurants, and regions described by the guideline, while its post-condition situation might be only constituted by the transplanted heart, its anatomical and morphological environment, the physiological functions in which it participates, and some physiological values. But the devices used during the transplantation and the surgeon can be external to the post-condition situation. This definition does not cover the possibility of a post-condition having constituents that are not involved in the description. This is a difficult issue. A possible solution is that such post-conditions are actually referenced by other descriptions that -for instance- 'control' the outcome of a procedure, or 'reconstruct' a set of events under an independent unity criterion. If this solution is applicable, such post-conditions would be maximal situations requiring the composition (bundle) of two or more related descriptions.
We define a disposition relation between the roles used in a plan having a main goal, and the influenced goal.For example, the role 'eater' can have a disposition to being satiated, meaning that a person playing the role of eater that adopts that plan can act in order to be satiated.Disposition relation is useful to account for those cases in which a task addressed by a role is not internal to the plan, but the plan is a subplan of another one in which that task is represented as a full-fledged goal.
Exit condition can be used to state what deliberation task causes to exit a cycle.
A task can be discarded within some plan. In this case, it is ignored in plan execution without affecting the satisfaction of the plan. A discarded task can appear only as a direct successor to a deliberation task.
iteration cardinality can be used to state in a task how many times an action should be repeated
A loop task with a defined number -and possibly frequency- of iterations.
A specialization of ending-task, aimed at sequencing events that end a plan execution without having reached its main-goal for a certain time
An activation task to start a plan execution after it has been suspended.
The task sequencing a decision activity, aiming at if action has to be taken in order to start a plan execution.
The task sequencing an activity from which the possibility is raised to execute a plan.
The task sequencing a positive decision to adopt a plan for execution.
The task joining the decision and preparation phases of the plan assessment, with the activation phases of the plan.
A beginning task is a control task that is the predecessor of all tasks defined in the plan.
The task sequencing a decision to take action in order to start a plan execution.
The task sequencing an assessment that the activities aiming at creating the prerequisites to start a plan execution are completed.
An ending task is a control task that has no successor tasks defined in the plan.
The task sequencing a negative decision to adopt a plan execution.
A specialization of ending-task, aimed at sequencing events that end a plan execution having reached its main-goal.
A loop task, which specifies when a certain condition becomes true for a cyclical task to exit.
A control task aimed at starting an activity. It is specialized either by a beginning task or a reactivation task.
A specialization of ending-task, aimed at sequencing events that end a plan execution without having reached its main-goal, and with no intention to resurrect the plan.
A loop task is a control task that has as successor an action -or complex- task that sequences at least two distinct activities sharing a minimal common set of properties -they have a MinimalCommonType. Notice that MinimalCommonType cannot be formalised as a first-order predicate, and then neither in OWL-DL. It can be considered a trivial guideline: when sequencing looped actions, choose a definite action class from the ground ontology. Some relations typically hold for loop tasks. Exit condition can be used to state what deliberation task causes to exit the cycle; iteration interval can be used to state how much time should be taken by each iteration of the looped activity; iteration cardinality can be used to state how many times the action should be repeated.
A specialization of ending-task, aimed at sequencing events that end a plan execution without having reached its main-goal, but with the possibility or resurrecting the plan.