Dynamic Epistemic Logic

Definition

Dynamic epistemic logic studies how agents’ knowledge changes after informational events such as announcements, observations, queries, or other model updates.

Why It Matters

Multi-agent systems often change because agents learn, communicate, observe actions, or update shared institutions. DEL-style update semantics provides a precise way to reason about those changes.

Formalism / Key Objects

• A basic epistemic model is a Kripke model with worlds, epistemic accessibility relations, and a valuation.
• Dynamic operators such as [event]phi mean that after the event update, phi holds.
• In Dolgorukov2024 - Dynamic Epistemic Logic of Resource Bounded Information Mining Agents, the update [?^A_G]phi means that group G performs a semi-public query about proposition formula A.
• In Galimullin2025 - Changing the Rules of the Game, DEL-like update modalities are applied to concurrent game models rather than ordinary epistemic models.

Connections

• Semi-Public Query Logic is a resource-bounded DEL where query costs and budgets constrain possible information acquisition.
• Alternating-Time Temporal Logic connects to DEL when strategic models are themselves updated.
• Strategic Reasoning benefits from DEL when agents reason about what others know after communication or institutional change.

Common Confusions

• DEL is not only public announcement logic; public announcements are one update type among many.
• A model update can change epistemic accessibility, valuations, transitions, or even model structure depending on the logic.
• Knowing that a query happened is different from knowing the answer to the query.

Key Sources

• Dolgorukov2024 - Dynamic Epistemic Logic of Resource Bounded Information Mining Agents
• Galimullin2025 - Changing the Rules of the Game