ALETHEIA, epistemic planner
Planning over dynamic epistemic logic in S5n and KD45n frames. Presented at ICAPS 2026.- C++23
Detail
Classical planning assumes that the agent knows which propositions hold; epistemic planning drops this assumption. The search space consists of pointed Kripke models, each of which must be updated, minimised and compared in full at every node, and goals may be irreducibly modal, for instance that an agent knows the door is open. Performance therefore reduces to three questions: how a Kripke model is represented, how modal formulas are evaluated over it, and how two models are recognised as the same epistemic situation.
Three decisions determine the design. A model is stored as three flat arrays of 64-bit words, for valuation, accessibility and designation, so that modal operators are word-parallel set operations. Formulas are evaluated as extensions: for each subformula the set of worlds where it holds is computed bottom-up and memoised on hash-consed formula identity, which reduces common knowledge to a single greatest fixpoint. Bisimulation contraction assigns world indices in an order determined by the model's structure alone, so bisimilar states serialise identically and duplicate detection is a comparison of 128-bit fingerprints.
| Before | After | |
|---|---|---|
| Largest solved instance, wall clock | 151 s | 40 ms |
| Resident memory on that instance | 21 GB | 7.3 MB |
| AND-OR search throughput | n/a | 19.8× |
Validated against the IεPC 2026 benchmarks, Tracks Basic and Intermediate. Built at UNAM-FI and IPN-ESCOM.