Klassdiagram

Klassdiagram, in UML terminology class diagram, is a type of static structure diagram that models the data structure of a software system. It shows the system's classes, their attributes and operations, and the relationships among classes. Class diagrams are a central tool in object-oriented design and are used to visualize the structure before and during implementation.

Elements: A class is represented by a rectangular box divided into three compartments: the class name, attributes, and operations (methods). Attributes specify name, type, and visibility; operations specify name, parameters, return type, and visibility. Relationships include associations (links between classes), aggregations and compositions (whole–part relationships), generalizations (inheritance), and realizations (interfaces).

Notations: Multiplicity on association ends indicates how many instances can participate (for example 1, 0..*, M..N). Navigability can be indicated by arrowheads. Inheritance is shown with a hollow triangle pointing to the parent class; interfaces are realized by a dashed line with a hollow triangle. Composition uses a filled diamond; aggregation uses an empty diamond.

Uses: Class diagrams document and design the static structure of a system, support code generation and reverse engineering, and serve as a reference for maintenance. They are commonly kept up-to-date as part of documentation in software projects and can be complemented by other UML diagrams such as sequence or activity diagrams.

Notes: Class diagrams focus on structure rather than behavior; for dynamic behavior, sequence or state diagrams are used in conjunction. The term Klassdiagramm is used in German-speaking contexts, while the English term is class diagram.