Composition Aggregation

• Stronger variety of Aggregation
• Part object may belong to only one whole object
• Parts live and die with the whole object
• Any deletion of whole cascades down to parts
• The multiplicity on the whole side must be 0 or one (0..1), but the multiplicity on the part side may be any interval (0..*)
• A composition Aggregation forms a tree of parts.
• 3 Notations: one solid diamond for each part, or one solid diamond as root of the tree of parts, or all parts inside the whole class