Generalization:
Definition: Generalization is like combining two or more similar things to create a more general and abstract things.
Example: Think of different types of bank accounts like savings and current accounts. Generalization in this context would create a higher-level entity called “Account” that encompasses both savings and current accounts. It’s like saying, “These are all types of accounts.”
Specialization:
- Definition: Specialization is the opposite; it’s breaking down a general thing into more specific parts.
- Example: Consider a general category like “Person.” Specialization in this case would create two lower-level entities called “Employee” and “Customer.” It’s breaking down the general concept of a person into more specific roles.
Aggregation:
- Definition: Aggregation is treating relationships between things as if they are things themselves.
- Example: Imagine there’s a relationship between employees, branches, and jobs. Aggregation would create a higher-level entity called ‘works on’ to represent this relationship. Additionally, you might have another relationship called ‘Manages’ between ‘works on’ and ‘manager,’ indicating who manages what tasks.
Comparison:
| Aspect | Generalization | Specialization | Aggregation |
|---|---|---|---|
| Process Type | Bottom-up approach | Top-down approach | Abstraction |
| Purpose | Combine common attributes of lower-level entities | Break down a higher-level entity into two or more lower-level entities | Treat relationships as higher-level entities |
| Effect on Schema Size | Reduces the schema size | Increases the schema size | Increases the schema size |
| Application Scope | Applied to a group of entities | Applied to a single entity | Applied to a group of relationships |
| Relationship with Entities | Common attributes form a new higher-level entity | Higher-level entity is broken down into lower-level entities | Relationships are treated as higher-level entities, participating in another relationship set |