Invited Speakers

Catarina Dutilh Novaes

Catarina Dutilh Novaes is a professor and University Research Chair at the Department of Philosophy of the VU Amsterdam. Before that, she was a professor and Rosalind Franklin fellow at the Department of Theoretical Philosophy of the Faculty of Philosophy of the University of Groningen (2011-2018). She is also a Professorial Fellow at Arché in St. Andrews (2019-2024), an external member of the Munich Center for Mathematical Philosophy. From 2017 to 2020 she was one of the Editors-in-Chief of Synthese. She is currently running the ERC Consolidator project 'The Social Epistemology of Argumentation' (2018-2023).

Her main fields of research are history and philosophy of logic, philosophy of mathematics, and social epistemology. She also has general interests in medieval philosophy, philosophy of psychology and cognitive science, general philosophy of science, philosophy of mind, issues pertaining to gender and race, and empirically-informed approaches to philosophy in general.


The Dialogical Roots of Deduction

In this talk, I offer a précis of my recently published book The Dialogical Roots of Deduction (CUP, 2020). The book offers an account of the concept and practices of deduction by bringing together perspectives from philosophy, history, psychology and cognitive science, and mathematical practice. I draw on all of these perspectives to argue for an overarching conceptualization of deduction as a dialogical practice: deduction has dialogical roots, and these dialogical roots are still largely present both in theories and in practices of deduction. The account also highlights the deeply human and in fact social nature of deduction, as embedded in actual human practices.


Santiago Figueira

Santiago Figueira is professor at the Computer Science Department of the University of Buenos Aires, and researcher at CONICET, Argentina. His research focuses on algorithmic randomness and its relationship to computability, and various aspects of computational logics with applications to the theory of databases. More recently, he began to study connections between quantum information and computability, and applications of the minimum description length principle in some studies on human cognition.

Finite Controllability for Ontology-Mediated Query Answering of CRPQ


Finite ontology mediated query answering (FOMQA) is the variant of ontology mediated query answering (OMQA) where the represented world is assumed to be finite, and thus only finite models of the ontology are considered. We study the property of finite-controllability, that is, whether FOMQA and OMQA are equivalent, for fragments of C2RPQ, the language of conjunctive two-way regular path queries, which can be regarded as the result of adding simple recursion to Conjunctive Queries.

For graph classes S, we consider fragments C2RPQ(S) of C2RPQ as the queries whose underlying graph structure is in S. We completely classify the finitely controllable and non-finitely controllable fragments under: inclusion dependencies, (frontier-)guarded rules, frontier-one rules (either with or without constants), and more generally under guarded-negation first-order constraints. For the finitely controllable fragments, we show a reduction to the satisfiability problem for guarded-negation first-order logic, yielding a 2EXPTIME algorithm (in combined complexity) for the corresponding (F)OMQA problem.

This is a joint work with Diego Figueira and Edwin Pin Baque.


Andreas Herzig

Andreas Herzig is a CNRS researcher of the Institut de Recherche en Informatique de Toulouse (IRIT) in Toulouse, France. He is the editor-in-chief of the Journal Applied Non-Classical Logics. He is an associate editor of Artificial Intelligence and a member of the editorial Board of the J. of Philosophical Logic (JPL).He is a fellow of the European Association for AI (EurAI).

Belief, knowledge and common knowledge about a proposition


Since Hintikka's seminal work the focus of epistemic logics is on the modalities `belief that' and `knowledge that'. Instead, I adopt the perspective of the less studied `belief about' and `knowledge about' modalities (the latter being more commonly called `knowledge whether').

In the first part of the talk I study the interplay between knowledge and common knowledge. I understand `common knowledge about p' as `either common knowledge that p or common knowledge that not p'. The other way round, `common knowledge that p' can be defined as `p and common knowledge about p'. Relying on that one can formulate an elegant alternative to the induction axiom: if there is common knowledge that each agent has knowledge about p then there is common knowledge about p. The axiom is sound for knowledge (but unsound for belief) and is complete for S5 knowledge.

In the second part of the talk I study the interplay between knowledge and belief. I assume a strong form of belief that satisfies the principle `belief implies belief to know'. I propose a more fine-grained analysis of `belief about' and `knowledge about', distinguishing `true belief about' and `mere belief about'. One of the benefits of this basis is an elegant characterisation of epistemic-doxastic situations.

In the last part of the talk I show that `belief about’ and `knowledge about’ modalities naturally lead to the definition of fragments of epistemic logic whose satisfiability problem is in NP. I argue that they are more interesting for knowledge representation than existing lightweight fragments.

Cláudia Nalon

Cláudia Nalon is an associate professor at the Department of Computer Science at the University of Brasília. She's interested in proof methods for combined modal logics, in particular when the resulting language allows for interaction between its components. Her PhD was about a resolution-based method for a particular interaction (no learning) between a linear-time temporal logic and multi-modal S5. She has also worked on tableau-based methods for temporal logics of knowledge with either no learning or perfect recall. She's interested in both the theoretical foundations and implementation of reasoning tools for normal modal logics and has worked on proof methods for languages that extend the basic normal modal logic K (allowing symmetry, reflexivity, seriality, transitivity, Euclideaness, and also parametrised multi-modal confluent logics). Very recently, she has worked on a resolution method for Coalition Logics, a non-normal modal logic for reasoning about cooperative agency.

From Global to Local: Efficient Reductions for Automatic Deduction in Modal Logics

(Joint work with Fabio Papacchini, Ullrich Hustadt, and Clare Dixon)


Modal logics are formalisms that can be used to represent complex situations in several fields, from the formalisation of the foundations of mathematics to applications in engineering. Due their broad applicability, it is desirable to have tools that perform automatic reasoning in order to prove (or verify) properties of specified systems. Automated reasoning for modal logics often exploits the fact that their languages can be translated into stronger logics, as first-order logic, for which there are readily available, reliable provers. In this talk, we will argue in the other direction: many modal logics can also be efficiently translated into weaker logics whilst preserving decidability. Our work is inspired by the well-known reductions from global consequence into local consequence that are given by Kracht, but provides shorter translations directly into a clausal normal form which is suitable for automatic reasoning using modal resolution. Experimental evaluation shows that we achieve better performance for the logics that extend K with axioms B, D, T, 4, and 5.