
513Reasoning About Agent Types and the Hardest Logic Puzzle EverMinds and Machines 23 (1): 123161. 2013.In this paper, we first propose a simple formal language to specify types of agents in terms of necessary conditions for their announcements. Based on this language, types of agents are treated as ‘firstclass citizens’ and studied extensively in various dynamic epistemic frameworks which are suitable for reasoning about knowledge and agent types via announcements and questions. To demonstrate our approach, we discuss various versions of Smullyan’s Knights and Knaves puzzles, including the Harde…Read more

100We look at lying as an act of communication, where (i) the proposition that is communicated is not true, (ii) the utterer of the lie knows that what she communicates is not true, and (iii) the utterer of the lie intends the lie to be taken as truth. Rather than dwell on the moral issues, we provide a sketch of what goes on logically when a lie is communicated. We present a complete logic of manipulative updating, to analyse the effects of lying in public discourse. Next, we turn to the study of …Read more

66This paper shows how propositional dynamic logic can be interpreted as a logic for multiagent belief revision. For that we revise and extend the logic of communication and change of [9]. Like LCC, our logic uses PDL as a base epistemic language. Unlike LCC, we start out from agent plausibilities, add their converses, and build knowledge and belief operators from these with the PDL constructs. We extend the update mechanism of LCC to an update mechanism that handles belief change as relation sub…Read more

57Composing modelsJournal of Applied NonClassical Logics 21 (34): 397425. 2011.• We study a new composition operation on (epistemic) multiagent models and update actions that takes vocabulary extensions into account

53On axiomatizations of public announcement logicSynthese 190 (S1). 2013.In the literature, different axiomatizations of Public Announcement Logic (PAL) have been proposed. Most of these axiomatizations share a “core set” of the socalled “reduction axioms”. In this paper, by designing nonstandard Kripke semantics for the language of PAL, we show that the proof system based on this core set of axioms does not completely axiomatize PAL without additional axioms and rules. In fact, many of the intuitive axioms and rules we took for granted could not be derived from th…Read more

51In this paper1, we develop an epistemic logic to specify and reason about the information flow on the underlying communication channels. By combining ideas from Dynamic Epistemic Logic (DEL) and Interpreted Systems (IS), our semantics offers a natural and neat way of modelling multiagent communication scenarios with different assumptions about the observational power of agents. We relate our logic to the standard DEL and IS..

50To know or not to know: epistemic approaches to security protocol verificationSynthese 177 (S1): 5176. 2010.Security properties naturally combine temporal aspects of protocols with aspects of knowledge of the agents. Since BANlogic, there have been several initiatives and attempts to incorpórate epistemics into the analysis of security protocols. In this paper, we give an overview of work in the field and present it in a unified perspective, with comparisons on technical subtleties that have been employed in different approaches. Also, we study to which degree the use of epistemics is essential for t…Read more

50Hidden protocols: Modifying our expectations in an evolving worldArtificial Intelligence 208 (1): 1840. 2014.When agents know a protocol, this leads them to have expectations about future observations. Agents can update their knowledge by matching their actual observations with the expected ones. They eliminate states where they do not match. In this paper, we study how agents perceive protocols that are not commonly known, and propose a semanticsdriven logical framework to reason about knowledge in such scenarios. In particular, we introduce the notion of epistemic expectation models and a propositio…Read more

38A logic of goaldirected knowing howSynthese 195 (10): 44194439. 2018.In this paper, we propose a decidable singleagent modal logic for reasoning about goaldirected “knowing how”, based on ideas from linguistics, philosophy, modal logic, and automated planning in AI. We first define a modal language to express “I know how to guarantee \ given \” with a semantics based not on standard epistemic models but on labeled transition systems that represent the agent’s knowledge of his own abilities. The semantics is inspired by conformant planning in AI. A sound and com…Read more

37Contingency and knowing whetherReview of Symbolic Logic 8 (1): 75107. 2015.A proposition is noncontingent, if it is necessarily true or it is necessarily false. In an epistemic context, ‘a proposition is noncontingent’ means that you know whether the proposition is true. In this paper, we study contingency logic with the noncontingency operator? but without the necessity operator 2. This logic is not a normal modal logic, because?→ is not valid. Contingency logic cannot define many usual frame properties, and its expressive power is weaker than that of basic modal logi…Read more

34True liesSynthese 195 (10): 45814615. 2013.A true lie is a lie that becomes true when announced. In a logic of announcements, where the announcing agent is not modelled, a true lie is a formula that becomes true when announced. We investigate true lies and other types of interaction between announced formulas, their preconditions and their postconditions, in the setting of Gerbrandy’s logic of believed announcements, wherein agents may have or obtain incorrect beliefs. Our results are on the satisfiability and validity of instantiations …Read more

24Knowing Your AbilityPhilosophical Forum 47 (34): 415423. 2016.In this article, we present an attempt to reconcile intellectualism and the antiintellectualist ability account of knowledgehow by reducing “S knows how to F” to, roughly speaking, “S knows that she has the ability to F demonstrated by a concrete way w.” More precisely, “S has a certain ability” is further formalized as the proposition that S can guarantee a certain goal by a concrete way w of some method under some precondition. Having the knowledge of our own ability, we can plan our future …Read more

15A New Framework for Epistemic LogicIn Proceedings of TARK 2017, Eptcs. pp. 515534. 2017.Recent years witnessed a growing interest in nonstandard epistemic logics of knowing whether, knowing how, knowing what, knowing why and so on. The new epistemic modalities introduced in those logics all share, in their semantics, the general schema of ∃x◻φ, e.g., knowing how to achieve φ roughly means that there exists a way such that you know that it is a way to ensure that φ. Moreover, the resulting logics are decidable. Inspired by those particular logics, in this work, we propose a very ge…Read more

7"Knowing value" logic as a normal modal logicIn Lev Beklemishev, Stéphane Demri & András Máté (eds.), Advances in Modal Logic, Volume 11, Csli Publications. pp. 362381. 2016.

6True liesSynthese 195 (10): 45814615. 2013.A true lie is a lie that becomes true when announced. In a logic of announcements, where the announcing agent is not modelled, a true lie is a formula that becomes true when announced. We investigate true lies and other types of interaction between announced formulas, their preconditions and their postconditions, in the setting of Gerbrandy’s logic of believed announcements, wherein agents may have or obtain incorrect beliefs. Our results are on the satisfiability and validity of instantiations …Read more

5Verifying epistemic protocols under common knowledgeProceedings of the 11th Conference on Theoretical Aspects of Rationality and Knowledge  Tark ’09 257266. 2009.Epistemic protocols are communication protocols aiming at transfer of knowledge in a controlled way. Typically, the preconditions or goals for protocol actions depend on the knowledge of agents, often in nested form. Informal epistemic protocol descriptions for muddy children, coordinated attack, dining cryptographers, Russian cards, secret key exchange are well known. The contribution of this paper is a formal study of a natural requirement on epistemic protocols, that the contents of the proto…Read more

3Representing Imperfect Information of Procedures with Hyper ModelsIn Mamata Banerjee & S. N. Krishna (eds.), Logic and Its Applications. ICLA 2015. Lecture Notes in Computer Science, vol 8923, Springer. 2015.© SpringerVerlag Berlin Heidelberg 2015. When reasoning about knowledge of procedures under imperfect information, the explicit representation of epistemic possibilities blows up the S5like models of standard epistemic logic. To overcome this drawback, in this paper, we propose a new logical framework based on compact models without epistemic accessibility relations for reasoning about knowledge of procedures. Inspired by the 3valued abstraction method in model checking, we introduce hyper mod…Read more

2Conditionally Knowing WhatIn Rajeev Goré, Barteld Kooi & Agi Kurucz (eds.), Advances in Modal Logic, Volume 10, Csli Publications. pp. 569587. 2014.

2Not All Those Who Wander Are Lost: Dynamic Epistemic Reasoning in NavigationIn Thomas Bolander, Torben Braüner, Silvio Ghilardi & Lawrence Moss (eds.), Advances in Modal Logic, Volume 9, Csli Publications. pp. 559580. 2012.

2Almost MecessaryIn Rajeev Goré, Barteld Kooi & Agi Kurucz (eds.), Advances in Modal Logic, Volume 10, Csli Publications. pp. 178196. 2014.

More for free: A dynamic epistemic framework for conformant planning over transition systemsJournal of Logic and Computation 27 (8): 23832410. 2017.© The Author, 2017. Published by Oxford University Press. All rights reserved. In this article, we introduce a lightweight dynamic epistemic logical framework for automated planning under initial uncertainty. We generalize the standard conformant planning problem in AI in two crucial aspects: first, the planning goal can be any formula expressed in an epistemic propositional dynamic logic ; second, procedural constraints of the desired plan specified by regular expressions can be imposed. We the…Read more

Beyond Knowing That: A New Generation of Epistemic LogicsIn Hans Van Ditmarsch & Gabriel Sandu (eds.), Jaakko Hintikka on Knowledge and Game Theoretical Semantics, Springer. pp. 499533. 2018.Epistemic logic has become a major field of philosophical logic ever since the groundbreaking work by Hintikka [58]. Despite its various successful applications in theoretical computer science, AI, and game theory, the technical development of the field has been mainly focusing on the propositional part, i.e., the propositional modal logics of “knowing that”. However, knowledge is expressed in everyday life by using various other locutions such as “knowing whether”, “knowing what”, “knowing how”…Read more
University of Amsterdam
PhD, 2010
Areas of Specialization
Modal and Intensional Logic 
Epistemic Logic 
Formal Epistemology 
Varieties of Knowledge 
Logic and Philosophy of Logic 