Associations - Composition and Aggregation - Aggregation

4 important questions on Associations - Composition and Aggregation - Aggregation

What is the AggregatonKind of an aggrgation?

The AggregationKind = Shared.

Why is the AggregationKind "Shared"?

We call it “shared” because the target end can be associated with of more than Book.

How do we read this diagram?

When you read an aggregation, you usually should just use “has.” We show an example of an aggregation/shared in Fig. 10.26.


A Book has many Authors



or


An Author is a shared part of many Books
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Unfortunately, as you might realize, the semantics of an aggregation is nearly identical to that of a  ....?


Unfortunately, as you might realize, the semantics of an aggregation is nearly identical to that of a regular association.

Anytime we use an aggregation, we could probably replace it with a plain association.

You should only use an aggregation if you want to emphasize a part-like relationship, but one that is not as strong as a composition.

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