Subclassification
According to the SysML 2.0 specifications, a definition is specialized using the subclassification relationship. Definition and usage elements can be specialized using several different kinds of specialization relationships. The specialized definition inherits the features of the more general definition element and can add other features. You can define subclass or superclass types to establish classification of system elements. Subclassification improves modularity and the structure of the systems design, and facilitates effective reuse of elements. In the following example, Vehicle is subclassified into Hybrid Truck and Full Electric Vehicle.
The Parts browser displays all the features that are inherited from the Hybrid Truck and Vehicle.
Creating a Subclassification relationship
You can create a Subclassification relationship in the following ways:
Create a Subclassification relationship from the diagram:
1. On the System Structure Diagram toolbar, click the Subclassification 
button.
button.2. On the diagram, click the source definition item and then click the target definition item. This creates a subclassification relationship on the diagram.