Representing relationships and roles

The VIVO ontology has made extensive use of what we have called "context nodes": nodes connecting one entity of primary interest with another but having attributes in their own right such as temporal bounds or a label and description for the connection.

With the ISF these have been brought together in a more formal structure of a reified relationship.  These relationships serve to link multiple entities, including roles, which under the Basic Formal Ontology (BFO) can only be realized through a temporally-bound process.

Here's a diagram, contrasting situations where roles are implicit and therefore not typically modeled, vs. the lower diagram, where a role is important to understanding the nature of the relationship between a person and an artistic work.