Whole-Part Relationship

A whole-part relationship indicates that one entity is composed of one or more parts which are themselves instances of that or another entity. Typically, a part can only be "attached" to one whole at a time. The parts can be said, in some very real way, to make up the whole.

In object-technology, whole-part or composition relationships have very specific meaning and use—typically denoting sole ownership over a set of object instances as well as certain copy, update, and delete semantics. In psychology and semantic modeling whole-part relationships reflect construction of larger entities out of smaller ones. These uses of the term are parallel to each other but not identical.

Example: A car is made up of a body, three or four wheels, a steering mechanism, a braking mechanism, and a power-train.

This is essentially a definition by parts for a car. In mechanical assemblages, the parts are the major subassemblies of the whole. In naturalistic objects, the parts are the major pieces into which a person would mentally dissect the object.

Last Modified January 2003. Send your comments?

©2002, 2003 John M. Artim