Keynote Speakers

Leila Amgoud (CNRS, France)

Leila Amgoud Title: Evaluation of Arguments: Foundations and Semantics
Abstract: Argumentation aims at increasing acceptability of claims by supporting them with arguments. Roughly speaking, an argument is a set of premises intended to establish a definite claim. Its strength depends on the plausibility of the premises, the nature of the link between the premises and claim, and the prior acceptability of the claim. It may generally be weakened by other arguments that undermine one or more of its three components. Evaluation of arguments is a crucial task, and a sizable amount of methods, called semantics, has been proposed in the literature. I will discuss two classifications of existing semantics: the first one is based on the type of semantics' outcomes (sets of arguments, weighting, and preorder), the second is based on the goals pursued by the semantics (acceptability, strength, coalitions). I will also discuss their theoretical foundations.

Bio: Leila Amgoud obtained a Ph.D and HdR in Artificial Intelligence from Paul Sabatier University respectively in July 1999 and June 2009. Before joining CNRS in 2001, She was a postdoctoral researcher at the university of Liverpool, UK. Her research interests lie within the broad area of knowledge representation and reasoning, in particular, Argumentation theory, Non-monotonic reasoning, Analogical reasoning, Practical reasoning, Decision making, Negotiation, Measuring inconsistency, Trust modelling, and Ranking systems.



Thomas Studer (University of Bern, Switzerland)

Thomas Studer Title: Modal and Justification Logics for Multi-agent Systems
Abstract: Epistemic modal logic is an important tool in the area of distributed and multi-agent systems. Recent work in this tradition includes, for instance, the study of the epistemic principles underlying blockchain mechanisms. Another current line of research is concerned with combinatorial topological models of distributed systems and the development of corresponding modal logics. They give rise to new notions of group knowledge as well as new epistemic dynamic principles. Modal logic cannot formalize the justifications underlying knowledge. This is remedied in justification logic. It replaces the ◻-modality from modal logic with explicit terms. That is, instead of formulas ◻φ, meaning φ is known, justification logic includes formulas of the form t : φ, meaning t represents a proof of φ. Originally, Artemov introduced justification logic to give a classical provability semantics to intuitionistic logic. Since then, justification logic has been adapted to many epistemic and deontic use cases. The first part of this talk deals with synergistic knowledge, a novel form of distributed knowledge. It is based on, which is joint work with Christian Cachin and David Lehnherr. The second part presents an epistemic model of zero-knowledge proofs in justification logic. It uses results from, which is joint work with David Lehnherr and Zoran Ognjanović.

Bio: Thomas Studer is a professor of Computer Science at the University of Bern, Switzerland where he heads the Logic and Theory Group. He studied computer science, mathematics, and philosophy and completed his Ph.D. in 2001 with a thesis on the mathematical modeling of object-oriented programming languages. His current research interests include modal logic and its applications as well as proof theory for computer science logic. Thomas Studer (co-)authored more than 70 research publications including two books. He is a presidium member of the Platform Mathematics, Astronomy, and Physics of the Swiss Academy of Sciences and serves on the board of the Swiss Society for Logic and Philosophy of Science. Negotiation, Measuring inconsistency, Trust modelling, and Ranking systems.



Yanjing Wang (Peking University, China)

Yanjing Wang Title: A Bundled Approach to Deontic Logic Abstract: In this talk, I will introduce a new semantic approach to deontic logic based on the so-called bundled modalities, which essentially pack a quantifier and a modality together. Our starting point is the observation that many "strange" logical behaviors of modalities and logical connectives in natural language are due to the fact that they have more complicated inner logical structures in the semantics. Many examples can be found in epistemic logics of know-wh, where the know-wh modalities often have the implicit ∃x◻ structure based on the mention-some interpretation. As the logical puzzles are abundant in deontic logic, a natural question arises: are there also some bundles hidden in the deontic modalities? Actually, the possibilities of viewing permissions and obligations as bundles were informally discussed by Hintikka in the early days of deontic logic. For example, Hintikka proposed to understand permission as a bundle of ∀x◇, i.e., an action type α is permitted iff every token of α is executable on some deontically ideal world. Given the techniques of the bundled modalities, we can flesh out this proposal formally, which results in a very desirable logic of free-choice permission satisfying most of the intuitive properties. Moreover, this semantics also predicts new logical behaviors not yet discussed in the literature. For example, according to our semantics, one of the four distributive laws is invalid, which aligns with our linguistic intuition. Besides the bundled modalities, our approach also features the Brouwer-Heyting-Kolmogorov (BHK) style treatment of propositions as action types inspired by intuitionistic logic. This opens the possibility of fine-grained control of the composition of action types in terms of non-classical connectives. It also reveals the subtleties behind the negation, conjunction, and implication in deontic logic. For example, we may discover different possible types of negations that matter in deontic logic, leading to different inter-definability between the deontic modalities.

Bio: Yanjing Wang obtained his Ph.D. in logic from the University of Amsterdam in 2010. He is currently a full professor of logic and vice-chair of the Department of Philosophy of Peking University. His research mainly focuses on modal logic and its applications in philosophy, theoretical computer science, and AI. He has published more than 60 English papers in leading international journals and top conference proceedings on logic, philosophy, and AI, such as The Review of Symbolic Logic, Annals of Pure and Applied Logic, Synthese, Artificial Intelligence, Advances in Modal Logic, TARK, IJCAI, AAMAS. In particular, Yanjing Wang is promoting a new research program of logics of knowing how, knowing why, knowing who, and so on. This also inspired him to propose a new class of well-behaved fragments of first-order modal logic by packing a quantifier and a modality together.