Learning Lifted STRIPS Models from Action Traces Alone: A Simple, General, and Scalable Solution

TL;DR

This paper introduces a scalable, sound, and complete method for learning STRIPS action models from action traces alone, capable of handling complex domains without restrictions on predicates.

Contribution

A novel, efficient test-based approach for learning lifted STRIPS models from traces that is general, scalable, and does not impose domain restrictions.

Findings

Method is theoretically sound and complete.

Successfully applied to large classical domains like the 8-puzzle.

Learnt models generalize well to larger instances.

Abstract

Learning STRIPS action models from action traces alone is a challenging problem as it involves learning the domain predicates as well. In this work, a novel approach is introduced which, like the well-known LOCM systems, is scalable, but like SAT approaches, is sound and complete. Furthermore, the approach is general and imposes no restrictions on the hidden domain or the number or arity of the predicates. The new learning method is based on an \emph{efficient, novel test} that checks whether the assumption that a predicate is affected by a set of action patterns, namely, actions with specific argument positions, is consistent with the traces. The predicates and action patterns that pass the test provide the basis for the learned domain that is then easily completed with preconditions and static predicates. The new method is studied theoretically and experimentally. For the latter, the method is evaluated on traces and graphs obtained from standard classical domains like the 8-puzzle, which involve hundreds of thousands of states and transitions. The learned representations are then verified on larger instances.