Aggregation and Composition

Aggregation and Composition



Aggregation; a whole-part relationship, such as the relationship between a breakfast and food items. In so far as you can add or remove food items and there would still be a meaningful relationship.

Similarly, the relationship between a degree and the courses studied,  where the degree is the whole and the courses studied is the part. You can add to or remove courses and the relationship still has meaning.

aggregations form a whole– part relationship and no object may be part of itself, directly or indirectly.

Composition; if the composing object is deleted, the composed objects must also be deleted. Such as a Window object, containing button object and various other objects such as labels etc. When the window object is deleted, so too are all the composed objects, the buttons and labels. (can the contained word be used here?).














a is Composition
b is Aggregation.