Speaker: Daniil Khaitovich (ILLC)
Date and Time: Thursday, September 7th 2023, 16:30-18:00
Venue: ILLC seminar room F1.15 in Science Park 107 and online
Title: Fixing group STIT logic
Abstract. STIT is a modal logic of agency to formalize statements of the form “agent i sees to it that φ”. One of its extensions, group STIT, allows to reason not only about individual agents, but about coalitions as well. The main advantage of that extension is its expressivity: it was shown that it is strictly more expressive than other popular multi-agent modal logics with coalitions such as Coalition logic or Alternating-time temporal logic. Nevertheless, it does not come for free: group STIT is neither decidable nor finitely axiomatizable.
During the talk, we will identify one conceptual problem with group STIT — the way groups and their actions are treated — and show the weaker version of logic to escape it, providing it with finite axiom system and proving its decidability as well. A number of connections with logic of dependence and relativized cylindric algebras will be shown as well.