Concepts of Generalization and Specialization in DBMS:
Generalization
Generalization is a bottom-up design approach in database modeling where two or more lower-level entity types are combined to form a higher-level (more general) entity type.
- This approach is used to abstract and represent shared characteristics among related entities at a higher level.
- A higher-level entity created through generalization can also be generalized further with other entities, allowing for multi-level abstraction.
- Generalization helps in reducing redundancy by grouping similar entities and defining shared characteristics at a higher level.
Example:
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:
Difference Between Generalization and Specialization:
| Generalization | Specialization |
|---|---|
| Generalization is a bottom-up approach where multiple lower-level entities are combined into a single higher-level entity. | Specialization is a top-down approach where a higher-level entity is divided into more specific lower-level entities. |
| In generalization, the goal is to abstract common attributes from different entities into a unified entity. | In specialization, the goal is to define new sub-entities with additional specific attributes not found in the general entity. |
| It reduces redundancy by centralizing shared attributes at a higher level. | It adds detail by allowing subtypes to include unique attributes beyond those in the general entity. |
| It starts from specific entities and works upward to create a more abstract entity. | It begins with a general entity and breaks it down into more specific and detailed entities. |
| An example of generalization is combining Car and Truck entities into a single Vehicle entity. | An example of specialization is dividing an Employee entity into FullTime_Employee and PartTime_Employee entities. |
