Tools used to create the diagram:
To understand more about the nomnoml tool and UML representation, please refer to this UML Representation article.
Association
It represents the relationship between two objects, which have their own lifecycle and no owner.
Example
Consider that Student and Teacher have objects. Here multiple students can associate with a single teacher and a single student can associate with multiple teachers. There is no ownership between these two objects.
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- [Student]<->[Teacher]
Aggregation
It represents the relationship of objects with their owners, like one object is the whole part or a part of another object
Example
Consider Department and Teacher have objects. Here a teacher belongs to muliple departments or is part of multiple departments. But when we delete, the Department Teacher object will not be destroyed.
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- [Teacher]-o[Department]
Composition
It represents the relationship of objects with parent/child relationship; i.e., child object is dependent on parent object
Example
A car has exactly one carburetor, and a carburetor is a part of one car. Carburetors cannot exist as separate parts, detached from a specific car.
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- [Carborator]-+[Car]
Dependency
It represents the relationship of objects where one object is dependent on another object.
Example
Client is dependent on server in web applications.
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- [Client]-->[Service]
Association types
- association-> association<-> association--> dependency<--> dependency-:> generalization<:- generalization--:> implementation<:-- implementation+- composition+-> compositiono- aggregationo-> aggregation-- note-/- hidden
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Conclusion
In this article, we learned about Association, Aggregation, Composition and Dependency relationships with UML diagrams.
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