  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.
