Active Generation of Logical Rules for POMCP Shielding

We consider the popular Partially Observable Monte-Carlo Planning (POMCP) algorithm and propose a methodology, called Active XPOMCP, for generating compact logical rules that represent properties of the control policy. These rules are then used as shields to prevent POMCP from selecting unexpected actions, with useful implications on the security and trustworthiness of the algorithm. Contrary to state-of-the-art methods, Active XPOMCP does not require a previously generated set of belief-action pairs to generate the logical rule, but it actively generates this data in an informationefficient way by querying the algorithm. Active XPOMCP reduces the number of beliefs needed to generate accurate rules with respect to state-of-the-art methods, and it allows to produce more accurate shields when few belief-action samples are available.