Who's the Expert? On Multi-source Belief Change

TL;DR

This paper introduces a logical framework for belief change involving multiple sources with varying expertise, addressing how to interpret reports about the world when sources may be unreliable due to lack of expertise.

Contribution

It extends propositional logic with expertise formulas to model and analyze belief updates considering sources' varying knowledge levels.

Findings

Proposed several postulates for belief change with multiple sources.

Developed concrete operators for belief merging based on the framework.

Analyzed operators' properties relative to the postulates.

Abstract

Consider the following belief change/merging scenario. A group of information sources gives a sequence of reports about the state of the world at various instances (e.g. different points in time). The true states at these instances are unknown to us. The sources have varying levels of expertise, also unknown to us, and may be knowledgeable on some topics but not others. This may cause sources to report false statements in areas they lack expertise. What should we believe on the basis of these reports? We provide a framework in which to explore this problem, based on an extension of propositional logic with expertise formulas. This extended language allows us to express beliefs about the state of the world at each instance, as well as beliefs about the expertise of each source. We propose several postulates, provide a couple of families of concrete operators, and analyse these operators with respect to the postulates.