A Containable is a kind of aggregate where an OsidObject is defined as a recursive composition of itself directly accessible without knowledge of the originating service.

Containables are rare because of the fulfillment of a recursive retrieval of OSID Ids. They are used only when independent references to a single container without its contained parts have no purpose and generic hierarchy services do not capture the meaning of the hierarchical structure.

Because of the hierarchical nature of Containables, sub-objects may be created for the sole purpose of creating the aggregate. It may be desirable to hide these building blocks from general view.