•  3
    © Springer-Verlag 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 3-valued abstraction method in model checking, we introduce hyper mod…Read more
  •  6
    True lies
    with Hans Ditmarsch and Thomas Ågotnes
    Synthese 195 (10): 4581-4615. 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
  •  50
    Hidden protocols: Modifying our expectations in an evolving world
    with Hans Van Ditmarsch, Sujata Ghosh, and Rineke Verbrugge
    Artificial Intelligence 208 (1): 18--40. 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 semantics-driven logical framework to reason about knowledge in such scenarios. In particular, we introduce the notion of epistemic expectation models and a propositio…Read more
  •  5
    Verifying epistemic protocols under common knowledge
    with Lakshmanan Kuppusamy and Jan van Eijck
    Proceedings of the 11th Conference on Theoretical Aspects of Rationality and Knowledge - Tark ’09 257--266. 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
  • More for free: A dynamic epistemic framework for conformant planning over transition systems
    with Yanjun Li and Quan Yu
    Journal of Logic and Computation 27 (8): 2383--2410. 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
  •  15
    Recent years witnessed a growing interest in non-standard 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
  • Beyond Knowing That: A New Generation of Epistemic Logics
    In Hans Van Ditmarsch & Gabriel Sandu (eds.), Jaakko Hintikka on Knowledge and Game Theoretical Semantics, Springer. pp. 499-533. 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
  •  7
    "Knowing value" logic as a normal modal logic
    with Tao Gu
    In Lev Beklemishev, Stéphane Demri & András Máté (eds.), Advances in Modal Logic, Volume 11, Csli Publications. pp. 362-381. 2016.
  •  2
    Conditionally Knowing What
    with Jie Fan
    In Rajeev Goré, Barteld Kooi & Agi Kurucz (eds.), Advances in Modal Logic, Volume 10, Csli Publications. pp. 569-587. 2014.
  •  2
    Almost Mecessary
    with Jie Fan and Hans van Ditmarsch
    In Rajeev Goré, Barteld Kooi & Agi Kurucz (eds.), Advances in Modal Logic, Volume 10, Csli Publications. pp. 178-196. 2014.
  •  2
    Not All Those Who Wander Are Lost: Dynamic Epistemic Reasoning in Navigation
    with Yanjun Li
    In Thomas Bolander, Torben Braüner, Silvio Ghilardi & Lawrence Moss (eds.), Advances in Modal Logic, Volume 9, Csli Publications. pp. 559-580. 2012.
  •  34
    True lies
    with Thomas Ågotnes and Hans van Ditmarsch
    Synthese 195 (10): 4581-4615. 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
  •  66
    This paper shows how propositional dynamic logic can be interpreted as a logic for multi-agent 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
  •  50
    To know or not to know: epistemic approaches to security protocol verification
    with Francien Dechesne
    Synthese 177 (S1): 51-76. 2010.
    Security properties naturally combine temporal aspects of protocols with aspects of knowledge of the agents. Since BAN-logic, 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
  •  53
    On axiomatizations of public announcement logic
    with Qinxiang Cao
    Synthese 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 so-called “reduction axioms”. In this paper, by designing non-standard 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
  •  24
    Knowing Your Ability
    with Tszyuen Lau
    Philosophical Forum 47 (3-4): 415-423. 2016.
    In this article, we present an attempt to reconcile intellectualism and the anti-intellectualist ability account of knowledge-how 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
  •  38
    A logic of goal-directed knowing how
    Synthese 195 (10): 4419-4439. 2018.
    In this paper, we propose a decidable single-agent modal logic for reasoning about goal-directed “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
  •  57
    Composing models
    with Jan van Eijck
    Journal of Applied Non-Classical Logics 21 (3-4): 397-425. 2011.
    • We study a new composition operation on (epistemic) multiagent models and update actions that takes vocabulary extensions into account
  •  513
    Reasoning About Agent Types and the Hardest Logic Puzzle Ever
    with Fenrong Liu
    Minds and Machines 23 (1): 123-161. 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 ‘first-class 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
  •  7
    Book Reviews (review)
    Studia Logica 102 (3): 647-654. 2014.
  • Epistemic Modelling and Protocol Dynamics
    Dissertation, University of Amsterdam. 2010.
  •  100
    On the logic of lying
    with Hans van Ditmarsch and Jan van Eijck
    We 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
  •  51
    In 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 multi-agent communication scenarios with different assumptions about the observational power of agents. We relate our logic to the standard DEL and IS..
  •  37
    Contingency and knowing whether
    with Jie Fan and Hans van Ditmarsch
    Review of Symbolic Logic 8 (1): 75-107. 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