Easily Memorize the 6 UML Class Diagram Relationships
UMLClass DiagramSoftware Engineering클래스 다이어그램소프트웨어 공학
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Published: 2025-07-05
Last modified: 2025-07-05
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Summary
Learn how to easily memorize the six types of UML class diagram relationships (Association, Dependency, Generalization, Realization, Composition, Aggregation) with a summary table.
The six relationships in UML class diagrams are crucial for understanding software design, but their similar terms can be confusing at first. Grouping similar concepts together and summarizing them in a table helps you grasp and memorize them at a glance.
UML Class Diagram Relationships Summary Table
There are 6 relationships in total, consisting of 2 strong/weak has-a relationships (Composition/Aggregation), 2 strong/weak uses-a relationships (Association/Dependency), 1 is-a relationship, and 1 can-do relationship (Generalization/Realization).
| Relationship | Core Concept | Keywords | Simple Example |
|---|---|---|---|
| Composition | Strong has-a | Shared Lifecycle, Essential Part (Composition) | House and Room (If the house disappears, the room also disappears.) House [filled diamond] -> Room |
| Aggregation | Weak has-a | Independent Lifecycle, Optional Part | Department and Student (Even if the department disappears, the student doesn't disappear.) Department(whole) [empty diamond] -> Student(part) |
| Association | Strong uses-a | Member Variable, Lasting Relationship | Soccer Team and Striker (The soccer team always uses the striker.) Soccer Team -> Striker |
| Dependency | Weak uses-a | Method Parameter, Brief Use | Developer and Book (The developer uses the book briefly.) Developer --> Book |
| Generalization | is-a (Inheritance) | Inheritance, Parent-Child | Cat is an Animal. (Animal is more general than cat. Divided into superclass(animal) and subclass(cat), Animal <- Cat) |
| Realization | can-do (Implementation) | Interface, Fulfilling a contract | Robot can clean. (Grouped by 'capability' to clean. 'Can clean' <-- 'Person') |