  In this paper, we present an Ontology Design Pattern for representing
situations that recur at regular periods and share some invariant factors,
which unify them conceptually: we refer to this set of recurring situations as
recurrent situation series. The proposed pattern appears to be foundational,
since it can be generalised for modelling the top-level domain-independent
concept of recurrence, which is strictly associated with invariance. The
pattern reuses other foundational patterns such as Collection, Description and
Situation, Classification, Sequence. Indeed, a recurrent situation series is
formalised as both a collection of situations occurring regularly over time and
unified according to some properties that are common to all the members, and a
situation itself, which provides a relational context to its members that
satisfy a reference description. Besides including some exemplifying instances
of this pattern, we show how it has been implemented and specialised to model
recurrent cultural events and ceremonies in ArCo, the Knowledge Graph of
Italian cultural heritage.
