Events

An event is something that happens at a place and time. An actor is an entity that participates in an event in some way. Events can be linked by chains of cause and effect. Events provide explanations of who did what; where, when and why.

We can consider events at various scales, with ‘larger’ events composed of ‘smaller’ ones. For example, considering a war as a collection of battles.

Events have labels that name or describe them, and that can be used in explanation. For example,

The assassination of Archduke Franz Ferdinand started World War I.

Whether this explanation is correct is arguable. Instead, we might prefer

The assassination of Archduke Franz Ferdinand prompted the Austrian ultimatum to Serbia.

as part of a much longer chain of cause and effect leading to World War I.

Chronology

The basic idea is to model events in a way that supports reasoning about time.

We consider the ‘when’ aspect of an event in one of two ways; either as an instant or an interval. An instant is a point in time. An interval is a duration of time that may have instants or other intervals within it, and that may overlap with other intervals. An interval has a beginning and an end, both of which are instants. We don’t have to be precise about the time of an instant. For example, we might say World War I is an interval that starts in the year 1914, without saying on which day. This is treating 1914 as though it were an instant. More precisely, it is saying that the start of World War I is inside the interval between 1st January and 31st December 1914.

We use the OWL-Time ontology to model the times of events. This gives all the flexibility we need in terms of modelling time; and it also allows us to start constructing event objects and reasoning about them before we have complete information. For example, we can say ‘World War I’ is an event that covers the interval ‘start of World War I’ to ‘end of World War I’ without knowing the dates. We can assert relationships to other events, such as World War I is ‘interval before’ World War II (i.e. WW1 ended before WW2 began), and reason about them. Later, we might discover and add the information that ‘start of World War I’ is in the year 1914 - and we can check this is consistent with the ‘interval before’ relationship we asserted earlier.

Places and Actors

We are interested in where events happen, the roles that actors play in events; and we want to classify and collate events by type. We will use the Information Exchange Standard (IES4) for these purposes.