UML

Multiplicity in class diagram should be indicated at each end of the association. This specifies the minimum and maximum number of instances that can be linked. For example, a car has 3 or 4 wheels, but each wheel belongs to exactly one car. Place multiplicity notations near the ends of an association. These symbols indicate the number of instances of one class linked to one instance of the other class.

There are six main types of relationships between classes: inheritance , realization / implementation , composition , aggregation , association, and dependency .

A use case diagram is a Unified Modeling Language (UML) diagram for requirements elicitation. Use case diagrams provide a graphical overview of the goals (modeled by use cases) that users (represented by actors) want to achieve by using the system. Use cases in a use case diagram can be organized and arranged according to their relevance, level of abstraction, and impact on the user. They can be linked to show their dependencies, include, extend, generation relationships.