In a model, the relationship according to which one object exists only within the context of a parent object. In this relationship there can be a one to many ratio of parent objects to child objects, but only a 1:1 ration between a child object and its parent. For example, any given logical drive can only belong to one computer, though a single computer may have multiple logical drives. Also, the logical drive must have a computer on which it exists, if the computer that hosts the logical drive ceases to exist, so does the logical drive itself.