How should aggregation and association be thought of

Question

Let's say we have a supermarket chain and a number of supermarkets belong to it.

If the chain ceases to exist the supermarkets will have to shut down. This could be implemented in UML using a composition relationship. On what side of the association should the filled-in diamond be located?

• Should it be like Chain----<.>supermarket ? Or chain<.>-----supermarket) ?
• Should I think of it as the supermarkets belong to the chain or the chain has supermarkets?

Answer 1

In UML, you put the composition diamond next to the class that composes another. In your example, An individual of type Chain composes [1] several individuals of type Supermarket, so the black diamond goes on the Chain end of the association.

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[1] Some people pronounce this "Chain has Supermarkets", which is indistinguishable from a different sense of the word "has", as in "Chain has name".