13+ Relationship Of Class Diagram. It provides a static view of the system. Generalization is not an association because it is a relation between the classes themselves, not between their instances (objects).
They work according to the principles of object orientation. So why not just code up that algorithm rather than drawing it as a sequence diagram? (relationship between item and other classes).
Unified modeling language (uml) calls them structure diagrams.
13+ Relationship Of Class Diagram. A class diagram shows types and subtype. Order class is an abstract class and it has two concrete classes. However, as your system scales and grows, it becomes increasingly difficult to keep track of all these summary of types of relationships and their notation. Class diagram defines the types of objects in the system and the different types of relationships that exist among them.