Differentiable Learning of Lifted Action Schemas for Classical Planning
Pith reviewed 2026-05-14 19:37 UTC · model grok-4.3
The pith
A differentiable neural network learns lifted action schemas from fully observed state traces by inferring unobserved action arguments from state changes.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
The central discovery is a novel neural network architecture that learns lifted action schemas from state traces where states are fully observed but action arguments are unobserved, by simultaneously identifying the arguments from state changes and learning the schemas such that the ground-truth structure is recovered in various planning domains.
What carries the argument
A differentiable neural network that processes sequences of states to infer action arguments and learn the corresponding lifted action schemas that add or delete atoms.
If this is right
- The learned schemas enable effective planning in large deterministic MDPs represented in STRIPS or PDDL.
- The architecture can be integrated into neuro-symbolic models for learning from more complex data like images.
- Recovery of ground-truth structure holds across various planning domains.
- The method shows robustness to observation noise.
- It handles variations related to slot-based dynamics models.
Where Pith is reading between the lines
- If the schemas are learned perfectly, they could support structural generalization to infinitely many domain instances.
- This approach might serve as a building block for learning planning domains directly from sequences of images and action labels.
- Extensions could address cases with partial state observations or ambiguous action effects.
- Integration with reinforcement learning could allow learning relational dynamics from experience.
Load-bearing premise
States are fully observed as sets of atoms and action arguments can be uniquely recovered from observed state changes without ambiguity or additional supervision.
What would settle it
Running the architecture on standard planning domains such as blocks world and observing whether the learned schemas match the ground-truth lifted representations exactly when action arguments are hidden.
Figures
read the original abstract
Classical planners can effectively solve very large deterministic MDPs represented in STRIPS or PDDL where states are sets of atoms over objects and relations, and lifted action schemas add or delete these atoms. This compact representation yields strong search heuristics and provides an ideal setting for structural generalization, since lifted relations and action schemas give rise to infinitely many domain instances. A central challenge is to learn these relations and action schemas from data, and recent approaches have addressed this problem using different types of observations. In this work, we develop a novel neural network architecture for learning action schemas from traces where states are fully observed but action arguments are unobserved. The problem is a simplification but an important step towards learning planning domains from sequences of images and action labels, and we aim to solve this simplification in a nearly perfect manner. The challenge lies in learning the action schemas while simultaneously identifying the action arguments from observed state changes. Our approach yields a robust differentiable component that can then be integrated into larger neuro-symbolic models. We evaluate the architecture on various planning domains, where the learned lifted action schemas must recover the ground-truth structure. Additionally, we report experiments on robustness to observation noise and on a variation related to slot-based dynamics models.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper introduces a differentiable neural architecture to learn lifted action schemas for classical planning from traces in which states are fully observed as sets of atoms but action arguments are latent. The model simultaneously discovers the schema predicates and infers the argument bindings that explain each observed state transition; the central claim is that this recovers ground-truth lifted schemas nearly perfectly across standard planning domains while remaining robust to observation noise.
Significance. If the recoverability result holds under the stated assumptions, the work supplies a modular, differentiable primitive that can be embedded in larger neuro-symbolic planners, directly addressing the long-standing gap between perceptual input and compact STRIPS-style representations.
major comments (2)
- [Method and Experimental Evaluation] The central claim that the architecture recovers ground-truth structure 'nearly perfectly' rests on the premise that each observed transition admits a unique binding of the learned schema parameters to the observed objects. No formal argument is given that the chosen neural parameterization or loss eliminates symmetries (e.g., identical effects produced by distinct bindings under commutative actions or symmetric objects).
- [Experimental Evaluation] The experimental section reports high recovery rates but does not include controlled ablations that inject controlled ambiguity (partial observability, symmetric predicates, or multiple consistent bindings) and measure degradation in schema fidelity; without such tests the robustness claim remains under-supported.
minor comments (1)
- Notation for the slot-based dynamics variant and the precise form of the reconstruction loss could be clarified with an additional diagram or pseudocode block.
Simulated Author's Rebuttal
We thank the referee for the constructive comments. We address the major concerns point-by-point below, providing clarifications where possible and committing to revisions that strengthen the empirical support and discussion of the method.
read point-by-point responses
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Referee: [Method and Experimental Evaluation] The central claim that the architecture recovers ground-truth structure 'nearly perfectly' rests on the premise that each observed transition admits a unique binding of the learned schema parameters to the observed objects. No formal argument is given that the chosen neural parameterization or loss eliminates symmetries (e.g., identical effects produced by distinct bindings under commutative actions or symmetric objects).
Authors: We acknowledge that the manuscript does not contain a formal proof that the neural parameterization and loss guarantee unique bindings in the presence of symmetries. The architecture relies on end-to-end optimization of a reconstruction loss over state transitions, which empirically selects the ground-truth schemas and bindings in the evaluated domains; the joint inference of schemas and argument bindings appears to break many symmetries because incorrect bindings produce inconsistent effects across multiple transitions. However, we agree this is an informal observation rather than a rigorous argument. In the revision we will add a dedicated discussion subsection that (i) explicitly identifies the symmetry issue, (ii) explains why the current loss and parameterization tend to avoid it in practice, and (iii) notes the conditions under which multiple bindings could remain consistent. revision: partial
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Referee: [Experimental Evaluation] The experimental section reports high recovery rates but does not include controlled ablations that inject controlled ambiguity (partial observability, symmetric predicates, or multiple consistent bindings) and measure degradation in schema fidelity; without such tests the robustness claim remains under-supported.
Authors: We agree that the current experimental section would be strengthened by controlled ablations that systematically introduce ambiguity. The existing noise-robustness experiments already vary observation noise, but they do not isolate symmetric predicates or multiple consistent bindings. We will add two new ablation studies in the revised manuscript: (1) domains containing commutative actions and symmetric objects, measuring schema recovery accuracy as a function of the degree of symmetry, and (2) a controlled test that forces the model to choose among multiple bindings that produce identical effects on a subset of transitions. These results will be reported alongside the existing tables to directly quantify degradation in schema fidelity. revision: yes
Circularity Check
No circularity: learning driven by external traces and ground-truth recovery
full rationale
The paper introduces a neural architecture to learn lifted action schemas from fully-observed state traces while recovering unobserved action arguments. Success is measured by fidelity to externally supplied ground-truth schemas on standard planning domains, with additional robustness experiments. No equation or claim reduces by construction to a fitted parameter, self-citation, or renamed input; the inverse problem of argument binding is solved via differentiable optimization against observed add/delete effects rather than by definitional fiat. The derivation therefore remains self-contained against external benchmarks.
Axiom & Free-Parameter Ledger
axioms (2)
- domain assumption States are fully observed as sets of atoms over objects and relations
- domain assumption Action arguments can be identified from observed state changes
discussion (0)
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