Generalization
Generalization is a bottom-up approach in which two or more lower-level entity types are combined to form a higher-level entity type.
- Also, the higher level entity can also combine with other lower level entities to make further higher level entity.
Example:
Consider the entities Car and Truck. Both can be generalized into a higher-level entity called Vehicle, which includes all the common attributes (like Vehicle_ID, Manufacturer, Model) that are shared by both Car and Truck.
- Generalization helps in reducing redundancy by grouping similar entities and defining shared characteristics at a higher level.
Specialization
Specialization is the reverse process of generalization. It is a “top-down” approach where a higher-level entity type is divided into two or more lower-level entities.
Example:
From the general entity Employee, we can specialize into subtypes like FullTime_Employee and PartTime_Employee. These subtypes inherit the general attributes of Employee (such as Employee_ID, Name), but each subtype has its own specific attributes (like Salary for FullTime_Employee and HourlyRate for PartTime_Employee).
- Specialization is used to add more detailed distinctions to a higher-level entity.
