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Sample-Efficient Learning of Probabilistic Causes for Reachability in Markov Decision Processes with Probabilistic Guarantees
Proceedings of the 42nd Conference on Uncertainty in Artificial Intelligence, PMLR 337:5168-5196, 2026.
Abstract
Probabilistic model checking for {Markov} decision processes ({MDPs}) provides quantitative guarantees, but often offers limited insight into why undesired outcomes occur. Probability-raising (PR) causality addresses this by identifying states whose visitation increases the probability of reaching designated states. Existing PR-cause identification methods, however, use {MDP} modifications ill-suited for learning: the gap between conditional and unconditional reachability probabilities can be hard to detect from samples, and construction requires reachability probabilities of the original {MDP}, which are unavailable when transition probabilities are unknown. We study unknown {MDPs} and propose a learning approach with probabilistic guarantees for PR-cause identification. Our key ingredient is a restart-based {MDP} modification that reduces PR-cause checking to two conditional reachability queries without using reachability values of the original {MDP}. We prove correctness, establish sample-complexity bounds, and develop an anytime learning-and-checking algorithm based on two-sided value iteration that progressively classifies states as causal, non-causal, or undecided. Experiments on two benchmarks demonstrate reliable and fast identification of PR causes.