LIRa session: René Mellema

Speaker: René Mellema

Date and Time: Thursday, September 12th 2019, 16:30-18:30

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

Title: An Inquisitive Dynamic Epistemic Logic with Factual Change.

Abstract. In many situations, we want to model the effect of actions on both the knowledge of others, and also what they want to know afterwards. For example, after you hear something fall in another room, you would not only want to know whether others heard that, but also if they want to know what fell down. In this talk we will present a logic for multi-agent modelling for these kinds of situations by combining two logical frameworks, the Logic of Communication and Change and the newer framework of Inquisitive Semantics. The latter is a framework that has been set up to give a reasonable formal interpretation to questions. From this field we will mostly use ideas from Action Model Logic with Issues. This allows us to build a logic where we can model knowledge, including common knowledge; the questions that agents want an answer to, including questions that are shared between agents; and epistemic events like public and private announcements and factual change, all in one logic.

This new logic is based on a new inquisitive epistemic logic for relativized group knowledge which we call Inquisitive Epistemic Propositional Dynamic Logic, based on PDL. We will present a sound and complete axiomatisation for this logic and discuss parts of its completeness proof. We enriched this logic with action models that also represent factual change. We call this resulting logic the Logic of Communication, Change, and Issues. We have shown that this logic can be completely reduced to its underlying static language and has a sound and complete axiomatisation.

This talk is based on my MSc thesis, which was done under the supervision of Rineke Verbrugge and Floris Roelofsen.