The relationship of class in UML

In theUML, a class diagram is a type of static structure diagram that describes the structure of a system by showing the system's classes, their attributes, and the relationships between the classes.

• Instance Level Relationships have Association, Aggregation and Composition.

  Composition is a special form of aggregation where in each part may belong to only one whole at a time. When the whole is destroyed, so are its parts. Aggregation is a special form of association as well that specifies a whole-part relationship between the aggregate (whole) and a component part.You state an association at the class level.Association is An association between classes indicates that objects of one class may be related to objects of the other class

• Class Level Relationships have generalization.

  The generalization relationship is also known as the inheritance or "is a" relationship.

• General Relationship have dependency.

  A dependency exists between two defined elements if a change to the definition of one would result in a change to the other. A dependency can be between instances, classes, or both.

Note:In the class diagram, there the arrow always point to the supplier.