"All the Things that Come and Go, Stop and Say Hello": Towards an ontological account of how participants enter and exit events

This paper presents an ontological account for how participants enter or exit events, based on a view of events as delimited by systems. With that, we introduce the notions of engaging and disengaging event as the events through which (respectively) an object becomes or ceases to be a participant of a main, external event by becoming or ceasing to be a component of the system that delimits this external event. We argue that it is a general type of event with many practical examples, which reveals a contextual facet of events and may shed light on the notion of roles for events.