Planning

how to represent things which stay unchanged after performing some action

-> a large number of so-called frame axioms would be needed in general to represent what does not change by performing an action.

the representation of implicit effects

e.g. if a car moves from one position to another, so does – any person in the car, the engine of the car, any dust particle in the car, any bacteria in the driver, etc.

required preconditions (the “qualifications”) ensuring that an action succeeds

• fully observable

• deterministic

• finite

• static (change happens only when the agent acts)

• discrete (in time, actions, objects, and effects)

literals can be propositional or first-order, but first-order literals must be ground (i.e., variable-free) and function-free.

The precondition:

a conjunction of function-free positive literals stating what must be true in a state before the action can be executed.

The effect: a conjunction of function-free literals (can be positive and negative) describing how the state changes when the action is executed.

(or progression planning): from initial state to goal

(or regression planning): from goal to initial state

allows to consider only relevant actions

(An action is relevant to a conjunctive goal if it achieves one of the conjuncts of the goal)

Forward and backward state-space search are particular forms of totally ordered plan searches.

-> They explore only strictly linear sequences of actions and do not take advantage of problem decomposition.

The goal test checks whether a plan is a solution to the original planning problem.

-> Because only consistent plans are generated, the goal test just needs to check that there are no open preconditions.