Special LIRa Session

Date and Time: Monday, May 27th 2019, 12:00-14:00

Venue: ILLC Seminar Room F1.15, Science Park 107.

Speaker #1: Adam Bjorndahl (Carnegie Mellon University)

Title: Measurement and Action.

Abstract. In previous work (in fact, work that was first presented in the LIRa seminar!), I introduced a topological generalization of Propositional Dynamic Logic in which program executions (or, more generally, actions) are represented as fundamentally deterministic, with nondeterminism emerging as an epistemic relationship between the agent and the system. In this talk, I will review how Dynamic Topological Logic can be used to represent these notions, with actions captured by functions and possible measurements by the topology. I will then motivate a generalization of this paradigm in which the distinction between action and measurement (i.e, between functions and opens) is erased, and sketch some preliminary definitions and results in this direction.

Speaker #2: Emiliano Lorini (CNRS, IRIT, Toulouse)

Title: Rethinking Epistemic Logic with Belief Bases.

Abstract. We introduce a semantics for a family of logics of explicit and implicit belief based on the concept of multi-agent belief base. Differently from standard semantics for epistemic logic in which the notions of possible world and doxastic/epistemic alternative are primitive, in our semantics they are non-primitive but are defined from the concept of belief base. We provide complete axiomatizations and prove decidability for our logics via finite model arguments. Furthermore, we provide polynomial embeddings of our logics into Fagin & Halpern’s logic of general awareness and establish complexity results via the embeddings. We present a number of dynamic extensions of the static framework by informative actions of both public and private type, including public announcement, belief base expansion and forgetting. Finally, we show how our belief base semantics for epistemic logic can be used to build the universal epistemic model, i.e., the epistemic model containing all possible belief hierarchies of the agents in the system.