Price of Privacy

Pavel Naumov and Jia Tao

The paper proposes a logical framework for reasoning about agents' ability to protect their privacy by hiding certain information from a privacy intruder. It is assumed that the knowledge of the intruder is derived from the observation of pieces of evidence and that there is a cost associated with the elimination of the evidence. 
The logical framework contains a modal operator labeled by a group of agents and a total budget available to this group. The key contribution of this work is the proposed incorporation of the cost factor into privacy protection reasoning within the standard modal logic framework. The main technical result are the soundness and completeness theorems for the introduced logical system with respect to a formally defined semantics. [pdf]

Knowledge in Communication Networks

Pavel Naumov and Jia Tao

The paper investigates epistemic properties of information flow under communication protocols with a given topological structure of the communication network. The main result is a sound and complete logical system that describes all such properties. The system consists of a variation of the multi-agent epistemic logic S5 extended by a new network-specific Gateway axiom. [pdf]

Budget-Constrained Knowledge in Multiagent Systems

Pavel Naumov and Jia Tao 

The paper introduces a modal logical system for reasoning about knowledge in which information available to agents might be constrained by the available budget. Although the system lacks an equivalent of the standard Negative Introspection axiom from epistemic logic S5, it is proven to be sound and complete with respect to an S5-like Kripke semantics. [pdf]

Logic of Confidence

Pavel Naumov and  Jia Tao

The article studies knowledge in multiagent systems where data available to the agents may have small errors. To reason about such uncertain knowledge, a formal semantics is introduced in which indistinguishability relations, commonly used in the semantics for epistemic logic S5, are replaced with metrics to capture how much two epistemic worlds are different from an agent’s point of view. The main result is a logical system sound and complete with respect to the proposed semantics. [pdf]

Symmetries and Epistemic Reasoning

Jeffrey Kane and Pavel Naumov

The paper studies epistemic properties of symmetric communication protocols. It proposes a logical system describing properties common to all protocols with the same group of symmetries. This system is an extension of the standard epistemic logic S5 by a new axiom, capturing properties of symmetry in the modal language. The main results are soundness and completeness theorems for this logical system. [pdf]

Epistemic Logic for Communication Chains

Jeffrey Kane and Pavel Naumov

The paper considers epistemic properties of linear communication chains. It describes a sound and complete logical system that, in addition to the standard axioms of S5 in a multi-modal language, contains two non-trivial axioms that capture the linear structure of communication chains. [pdf]