Generalization is a link that defines a relation between two classes. Using generalizations, you can model inheritance.
Child class has all properties and methods of parent class, plus it may add new behaviors. If you create a new class (class name doesn't exist), then it will be necessary to define an inheritance to more general classes from the core or its successors.
To create Generalization
Toad Data Modeler implements the concept of metamodels. Metamodels are accessible only in Expert Mode (via Package Explorer).
Metamodel is a graphical representation of objects, classes, methods and relationships between them in a specific Package.
Using metamodels, you can create your own classes, methods and properties and define relationships between those items and items that are created in the application by default.
Important: It is recommended to only use lower and uppercase letters for naming your objects in metamodels (no numbers and special characters).
Example: The metamodel of Oracle package
Associations and aggregations represent a relationship between two classes. If one class owns another class, then it's an aggregation. (Attribute has a Domain, Entity is owned by Model and Model has a list or collection of Entities etc.)
To create Associations / Aggregations