UML Class Diagrams IS 4 Athanasios Podaras Class

UML Class Diagrams_ IS 4 Athanasios Podaras

Class Diagrams vs ERDs Class diagrams and ERDs both illustrate a structural model of a system. Class diagram: it represents a dynamic view of a system (i. e. a database system) Structural features: Attributes, Name of a class Behavioural features. Methods or operations ERDs, depicting only structural features (Entity Name, Attributes) provide a static representation of the system.

Class Diagram concepts • Class: Structure of the system: Attributes, Multiplicity (Cardinality in ERD), Association (Relationship in ERD) between classes Behaviour: Operations (Methods) of a class

Advanced Class Diagram Concepts • Aggregation: “Has a” Relationship between classes. The general class Class 1“has a” second class but it the former may exist even without the latter(i. e. Project Team (Class 1 “has a” team member (Class 2), but it can exist with the rest of the team members). • Composition: “Is Composed of” Relationship. The same as aggregation, but in this case Class 1 cannot exist without Class 2 (i. e. motorcycle (class 1) “is composed of” an engine (Class 2) ). • Generalization: A relationship between a “parent” class and a “child class” Class 2 “is kind of a” Class 1 (General Class). (i. e. Sony is kind of a Television)

Comparison between a Class and an ERD (EXAMPLE)

Lierature • OMG(Object Management Group) (2017). Object Modeling with UML. Class Diagrams. Available at: http: //www. omg. org/news/meetings/workshops/presentations/eai_2 001/tutorial_monday/tockey_tutorial/4 -Class_Models. pdf