  Event Structures (ESs) are mainly concerned with the representation of causal
relationships between events, usually accompanied by other event relations
capturing conflicts and disabling. Among the most prominent variants of ESs are
Prime ESs, Bundle ESs, Stable ESs, and Dual ESs, which differ in their
causality models and event relations. Yet, some application domains require
further kinds of relations between events. Here, we add the possibility to
express priority relationships among events.
  We exemplify our approach on Prime, Bundle, Extended Bundle, and Dual ESs.
Technically, we enhance these variants in the same way. For each variant, we
then study the interference between priority and the other event relations.
From this, we extract the redundant priority pairs-notably differing for the
types of ESs-that enable us to provide a comparison between the extensions. We
also exhibit that priority considerably complicates the definition of partial
orders in ESs.
