Multi-Agent Only Knowing on Planet Kripke

International audienceThe idea of only knowing is a natural and intuitive notion to precisely capture the beliefs of a knowledge base. However, an extension to the many agent case, as would be needed in many applications , has been shown to be far from straightforward. For example, previous Kripke frame-based accounts appeal to proof-theoretic constructions like canonical models, while more recent works in the area abandoned Kripke semantics entirely. We propose a new account based on Moss' characteristic formulas, formulated for the usual Kripke semantics. This is shown to come with other benefits: the logic admits a group version of only knowing , and an operator for assessing the epistemic en-trenchment of what an agent or a group only knows is definable. Finally, the multi-agent only knowing operator is shown to be expressible with the cover modality of classical modal logic, which then allows us to obtain a completeness result for a fragment of the logic

What will they say?—Public Announcement Games

Dynamic epistemic logic describes the possible information-changingactions available to individual agents, and their knowledge pre- and post conditions.For example, public announcement logic describes actions in the form of public,truthful announcements. However, little research so far has considered describing andanalysing rational choice between such actions, i.e., predictingwhat rational self-interestedagents actually will or should do. Since the outcome of information exchangeultimately depends on the actions chosen by all the agents in the system, and assumingthat agents have preferences over such outcomes, this is a game theoretic scenario.This is, in our opinion, an interesting general research direction, combining logic andgame theory in the study of rational information exchange. In this article we take somefirst steps in this direction: we consider the case where available actions are publicannouncements, and where each agent has a (typically epistemic) goal formula thatshe would like to become true. What will each agent announce? The truth of the goalformula also depends on the announcements made by other agents. We analyse suchpublic announcement games

What will they say?—Public Announcement Games

Dynamic epistemic logic describes the possible information-changingactions available to individual agents, and their knowledge pre- and post conditions.For example, public announcement logic describes actions in the form of public,truthful announcements. However, little research so far has considered describing andanalysing rational choice between such actions, i.e., predictingwhat rational self-interestedagents actually will or should do. Since the outcome of information exchangeultimately depends on the actions chosen by all the agents in the system, and assumingthat agents have preferences over such outcomes, this is a game theoretic scenario.This is, in our opinion, an interesting general research direction, combining logic andgame theory in the study of rational information exchange. In this article we take somefirst steps in this direction: we consider the case where available actions are publicannouncements, and where each agent has a (typically epistemic) goal formula thatshe would like to become true. What will each agent announce? The truth of the goalformula also depends on the announcements made by other agents. We analyse suchpublic announcement games.publishedVersio

Linguistic and Cultural Competences in Dynamic Possible Worlds

Linguistic and Cultural Competences are closely linked, as they involve the ability to infer and trace truths within knowledge stored in memory. Humans respond to three interrelated questions: Logic, Epistemology, and Ontology. This paper defines a place for Cultural Competence within these philosophies through Epistemic Modal Logic and Dynamic Possible Worlds. Cultural Competence is crucial in social robots: pleasantness goes with it, but it also has practical functions, managing incomplete pieces of knowledge and shortening the customisation. The artificial agent simulates empathy and meta-cognition, enacting justified action plans that conform with ontology and its awareness thanks to the Euclidean S5 accessibility relation between possible worlds

Are two Dimensions Too Many? - A one-dimensional rival to two-dimensional semantics

We discuss two interpretations of two-dimensional semantics (2DMS) due to D. Chalmers and R. Stalnaker. The main problem with both interpretations of the formal framework is the relinquishng of rigidity for terms. They are in a sense unfaithful to an agent's beliefs. We present alternative principles to capture what we take to be agents's beliefs, namely: the principles of hyper-rigidity and backward reference to actuality. We propose then to go back to a one-dimensional semantics which affords a satisfactory model of beliefs reports. Our proposal, like 2DMS, addresses typical problems of representation for beliefs and epistemological difficulties related to modal knowledge

Approches légères pour le raisonnement sur les connaissances et les croyances

Dans cette thèse nous étudions un cadre simple dans lequel modéliser les croyances et les connaissances ainsi que leur évolution dans des systèmes multi-agents. La logique standard de représentation des connaissances est très expressive, mais au prix d'une haute complexité calculatoire. Nous proposons ici un cadre qui permet de capturer plus de situations que d'autres approches existantes tout en restant efficace. En particulier, nous considérons l'application de notre logique à la planification épistémique : étant données une situation initiale et des actions possibles, peut-on atteindre un but fixé ? Cela peut signifier savoir à qui poser des questions pour apprendre des informations, faire en sorte de ne pas être remarquée lorsque l'on lit le courrier de quelqu'un d'autre, ou empêcher quelqu'un d'entendre nos secrets. Nous considérons aussi de possibles extensions à des logiques de croyance, ainsi que les liens entre notre système et d'autres cadres proches.In this thesis we study a lightweight framework in which to model knowledge and beliefs and the evolution thereof in multiagent systems. The standard logic used for this is very expressive, but this comes at a high cost in terms of computational efficiency. We here propose a framework which captures more than other existing approaches while remaining cost-effective. In particular, we show its applicability to epistemic planning: given an initial situation and some possible actions, can we find a way to reach our desired goal? This might mean knowing who to ask in order to learn something, making sure we aren't seen when reading someone else's mail, or preventing someone from overhearing our secrets. We also discuss possible extensions to logics of belief, and the relations between our framework and other related approaches

Is meaning intrinsically normative?

I examine the deflationary view according to which meaning has normative implications but is not a normative property. I argue that, contrary to deflationism, meaning properties are normative but that they are not intrinsically so