The relationships resource type represents connections between resource objects in CDF. Relationships allow you to organize assets in other structures in addition to the standard hierarchical asset structure. Each relationship is between a source and a target object and is defined by a relationship type and the external IDs and resource types of the source and target objects. Optionally, a relationship can be time-constrained with a start and end time. To define and manage the available relationship types, use the labels resource type. The externalId field uniquely identifies each relationship.