In this paper we describe an Ontology Design Pattern for modeling events that recur regularly over time and share some invariant factors, which unify them conceptually. The proposed pattern appears to be foundational, since it models the top-level domain-independent concept of recurrence, as applied to a series of events: we refer to this type of events as recurrent event series. The pattern relies on existing patterns, i.e. Collection, Situation, Classification, Sequence. Indeed, a recurrent event is represented as both a collection of events and a situation in which these events are contextualized and unified according to one or more properties that are peculiar to each event, and occur at regular intervals. We show how this pattern has been used in the context of ArCo, the Knowledge Graph of Italian cultural heritage, in order to model recurrent cultural events, festivals, ceremonies.
