UML class diagram

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1 Definition

UML Class diagrams are one kind of official diagram types of the Unified modeling language (UML)

2 Architecture

Class diagrams are made with quite a complex "language".

2.1 Classes

  • Classes are represented with boxes
  • Represented by a rectangle with one, two or three "fields": classname, properties and methods
Relationships in class diagrams
Association
  • A relationship between instances of the two classes
  • Represented by: a solid line with an arrow, directed from the source class to the target class
Aggregation
  • A part-of relationship
  • Represented by:
  • Example: a learning object is part of an environment
Generalization
  • A is-a relationship
  • Represented by: A solid line with a triangular arrow from specialized class to class
  • Example: Learner is a role
Composition
  • Like aggregation but you can add more constraints.
  • An instance of a class can be potentially a component of several classes, but can only be owned by one.
Multiplicity
  • of an association end is the number of possible instances of the class associated with a single instance of the other end.
  • Represented on both ends by the following syntax
</tbody>
MultiplicitiesExplanation
0..1 zero or one instance. The notation n . . m indicates n to m instances.
0..*  or  * no limit on the number of instances (including none).
1 exactly one instance
1..* at least one instance
More
  • There is more ...

2.2 Properties of classes

3 Examples

3.1 IMS Learning Design