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Explain generalization, specialization and aggregation. OR Compare generalization, specialization and aggregation with suitable examples.


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.”


  • 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.


  • 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.


Process TypeBottom-up approachTop-down approachAbstraction
PurposeCombine common attributes of lower-level entitiesBreak down a higher-level entity into two or more lower-level entitiesTreat relationships as higher-level entities
Effect on Schema SizeReduces the schema sizeIncreases the schema sizeIncreases the schema size
Application ScopeApplied to a group of entitiesApplied to a single entityApplied to a group of relationships
Relationship with EntitiesCommon attributes form a new higher-level entityHigher-level entity is broken down into lower-level entitiesRelationships are treated as higher-level entities, participating in another relationship set

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