Yanjing Wang
Department of Philosophy Peking University
LORI
Publication Types:
Hypergraphs, local reasoning, and weakly aggregative modal logic
Abstract. This paper connects the following three apparently unrelated topics: an epistemic framework fighting logical omniscience, a class of generalized graphs without the arities of relations, and a family of nonnormal modal logic rejecting the aggregative axiom. Through neighborhood frames as their meeting point, we show that, among many completeness results obtained in this paper, the limit of a family of weakly aggregative logics is both exactly the modal logic of hypergraphs and also the epistemic logic of local reasoning with veracity and positive introspection, which also answers a question left open by Fagin and Halpern (1988). The logics studied are shown to be decidable based on a filtration construction.
Weakly Aggregative Modal Logic: Characterization and Interpolation
Abstract. Weakly Aggregative Modal Logic (WAML) is a collection of disguised polyadic modal logics with n-ary modalities whose arguments are all the same. WAML has some interesting applications on epistemic logic and logic of games, so we study some basic model theoretical aspects of WAML in this paper. Specically, we give a van Benthem-Rosen characterization theorem of WAML based on an intuitive notion of bisimulation and show that each basic WAML system Kn lacks Craig Interpolation.
Multi-agent knowing how via multi-step plans: a dynamic epistemic planning based approach
Abstract. There are currently two approaches to the logic of knowing how: the planning-based one and the coalition-based one. However, the rst is single-agent, and the second is based on single-step joint actions. In this paper, to overcome both limitations, we propose a multi-agent framework for the logic of knowing how, based on multi-step dynamic epistemic planning studied in the literature. We obtain a sound and com- plete axiomatization and show that the logic is decidable, although the corresponding multi-agent epistemic planning problem is undecidable.
Knowledge-now and Knowledge-all
Abstract: In this paper, we propose a logical framework extending the standard epistemic logic with a new knowledge operator $\G_i$ which captures the knowledge about (physically) necessary facts, e.g., scientific knowledge. Semantically, the truth of $\G_i\phi$ depends on not only the epistemically indistinguishable worlds from the current real world but also the relevant (physically) possible worlds which are clearly distinguishable. Essentially, $\G_i$ is a bundle of the standard epistemic modality and a necessity-like modality. We axiomatize the corresponding epistemic logic completely in single- and multi-agent cases with interesting interaction axioms between the two epistemic operators.
A logic of knowing how
Abstract: In this paper, we propose a single-agent modal logic framework for reasoning about goal-direct “knowing how” based on ideas from linguistics, philosophy, modal logic and automated planning. We first define a modal language to express “I know how to guarantee phi given $\psi$” with a semantics not based on standard epistemic models but labelled transition systems that represent the agent’s knowledge of his own abilities. A sound and complete proof system is given to capture the valid reasoning patterns about “knowing how” where the most important axiom suggests its compositional nature.
On axiomatizations of PAL
Abstract. In the literature, different axiomatizations of Public Announcement Logic (PAL) were proposed. Most of these axiomatizations share a ‘core set’ of the so-called reduction axioms. In particular, there is a composition axiom which stipulates how two consecutive announcements are composed into one. In this paper, by designing non-standard Kripke semantics for the language of PAL, we show that without the composition axiom the core set does not completely axiomatize PAL. In fact, most of the intuitive ‘axioms’ and rules we took for granted could not be derived from the core set. The non-standard semantics we proposed is of its own interest in modelling realistic agents. We show that with the help of different composition axioms we may axiomatize PAL w.r.t. such non-standard semantics.