# (Arbitrary) Partial Communication

## TL;DR

This paper explores a novel form of partial, topic-based communication in multi-agent systems within dynamic epistemic logic, analyzing its properties, complexity, and how it compares to public announcements, including an extension with quantification over topics.

## Contribution

It introduces a formal framework for topic-based partial communication, provides a complete axiomatisation, and compares its expressivity and complexity to public announcement models.

## Key findings

- Partial communication is incomparable to public announcements in update effects.
- Model checking for the extended language is PSPACE-complete.
- The new language's expressivity is incomparable to that of public announcements.

## Abstract

Communication within groups of agents has been lately the focus of research in dynamic epistemic logic (DEL). This paper studies a recently introduced form of partial (more precisely, topic-based) communication. This type of communication allows for modelling scenarios of multi-agent collaboration and negotiation, and it is particularly well-suited for situations in which sharing all information is not feasible/advisable. After presenting results on invariance and complexity of model checking, the paper compares partial communication to public announcements, probably the most well-known type of communication in DEL. It is shown that the settings are, update-wise, incomparable: there are scenarios in which the effect of a public announcement cannot be replicated by partial communication, and vice versa. Then, the paper shifts its attention to strategic topic-based communication. It does so by extending the language with a modality that quantifies over the topics the agents can `talk about'. For this new framework, it provides a complete axiomatisation, showing also that the new language's model checking problem is PSPACE-complete. The paper closes showing that, in terms of expressivity, this new language of arbitrary partial communication is incomparable to that of arbitrary public announcements.