The STRIPS representation is

Answer: STRIPS is an action-centric representation.

What STRIPS encodes: planning operators (actions) defined by their preconditions and effects.

• Operator structure: an operator has a name and parameters, a list of preconditions that must hold to apply the action, an add-list (positive effects) and a delete-list (negative effects).

• Example: move(?x, ?from, ?to) — Preconditions: at(?x, ?from), clear(?to); Add-list: at(?x, ?to), clear(?from); Delete-list: at(?x, ?from), clear(?to).

• Why action-centric: planning proceeds by selecting and sequencing operators to transform an initial state (set of predicates) into a goal state; the representation centers on these operators and their state-changing effects.

• Distinction from other descriptions: although STRIPS uses predicates to describe states, it is not primarily a feature-centric or hierarchical representation. Hierarchical planners decompose tasks into subtasks, which is a different paradigm from the flat operator model used in STRIPS.