UML aggregation vs association

Question

Here I am, with another question about aggregation and association. I wanted to learn some basics of UML, so I started reading \"UML distilled\" by Martin Fowler. I read bot

Answer 1

They do not mean the same! I can put it in this way:

Association relationship: A class references another class. Actually it shows that a class is related to another class but they don't necessarily have attributes to show this relationship... e.g 'Teacher' and 'Student' classes, although 'Teacher' class has no attribute that refer to students, but we do know that in reality a teacher do have students... And also 'School' class has 'teachers' and 'students' properties that now make those two classes related to each other.

Aggregation relationship: A class contains another class. But if the container(ClassRoom) is destroyed, the contained(Chair) is not. Actually the ClassRoom owns the Chair. Aggregation is a more stronger relationship than the Association relationship.

Here is also a tutorial about it and the whole UML2.0 which explains everything easy and simple, you may find it useful: https://github.com/imalitavakoli/learn-uml2

TIP: Also let me mention that because the Association relationship exists between classes most of the times, we sometimes don't draw it to prevent unnecessary complexity.