Decidability of unrestricted real-time policy change

Determine whether the PolicyChange* problem for arbitrary, not necessarily treelike, generic monitors and pMTL policies under real-time semantics is decidable.

Background

The paper defines PolicyChange* by removing the treelike-monitor restriction: given pMTL policies φ₁ and φ₂, the problem asks whether every generic monitor admits a state transformation implementing policy change from φ₁ to φ₂. For discrete-time semantics, the paper establishes decidability upper bounds: EXPSPACE for pLTL and 2EXPSPACE for pMTL. The corresponding real-time problem is not resolved. This question is distinct from the treelike case, for which the paper gives a decision procedure and complexity bounds.

References

Whether this problem is decidable for real-time semantics remains open.

— Policy Change for Treelike Monitors  (2609.10114 - Hublet et al., 9 Sep 2026) in Section 5, 'Policy Change for Non-Treelike Monitors' (immediately before Section 6, Conclusion)