This is a collection of objects that are bound together by a root entity, otherwise known as an aggregate root. The aggregate root guarantees the consistency of changes being made within the aggregate by forbidding external objects from holding references to its members.
The concept of the aggregate remains in FP; however, it is not represented in terms of a class. Instead, it can be expressed as a structure, including a set of aggregate states, initial state, set of commands, set of events, and function-mapping the set of commands to the set of events given a state. Cohesion is provided by a module mechanism.