One-to-many and aggregation

UML
1

I am having difficulty in undersand the difference between one-to-many association between two classes aggregation relationship betweeen two classes. Are they same? Can they overlap?

thanks

2

Hi pradeep,

Thanks for your post. In fact, they are not the same.
One-to-many association does not specify the characteristics of the relationship while aggregation does.
Aggregation is the part-of relationship. It’s like saying that a car has an engine and wheels as its part.

I hope this explanation can help. If you have any further inquiries, please feel free to ask.

Best regards,
Lilian Wong

3

Hi Wong,

If I have understood you well, then it means that if a PERSON has one-to many relationship with ADDRESS then, a PERSON’s characteristic is not defined or identified by ADDRESS. So A PERSON is not an aggregation of ADDRESS while a PERSON has one-to-many relationship with ADDRESS.

Thanks for the explanation. :slight_smile:

-pradeep

4

Hi pradeep,

Actually, aggregation specifies the characteristics of the relationship between two classes, but it is not necessary to be one-to-many relationship.

Will it be more clear? If there are any inquiries, please feel free to ask.

Best regards,
Lilian Wong

5

Hi pradeep,

The easiest way to remember aggregation ist, that it shows "has-a " relationship. It can be one-one, one-many or any other relationships.

Assiziation just defines, that classes have relationship.

I hope it will help.