Relationship is a special type of information resource that brings a number of pattern concerns to the forefront.  Relationships can involve like things (in the same ontological category) or unlike things.

General types of relationship include containment, composition (both part/whole and piece/whole), and hierarchical.  Hierarchical relationships can be created by generalizing intuitive things to a less intuitive level (individuals and some organizations generalized to "legal entity") by specializing things to more technical level (organization specialized as "government organization").

Certain relationships take on an even more important character.  Agreements (including contractual relationships), roles, and systems are singled out elsewhere in this ontology as high-level concepts in their own right.

Figure 20

Key relationships can involve individuals and/or organizations, and can provide structure to physical and information resource types.