    deferred class
    	EV_CONTAINABLE

    General
    	cluster: interface
    	description: "Abstraction for objects that may be parented."
    	keywords: "parentable, containable, child"

    Ancestors
    	EV_ANY*

    Queries
    	data: ANY
    	is_destroyed: BOOLEAN
    	parent: EV_ANY

    Commands
    	copy (other: [like Current] EV_CONTAINABLE)
    	destroy
    	set_data (some_data: [like data] ANY)