Generalization and Aggregation.
1 Answer


Generalization is a abstracting process of viewing sets of objects as a single general class by concentrating on the general characteristics of the constituent sets while suppressing or ignoring their differences. In simple terms, Generalization is a process of extracting common characteristics from two or more classes and combining them into a generalized superclass. So, it is a bottom up approach as two or lower level entities are combined to form a higher level entity. The common characteristics means here attributes or methods.

Notation of Generalization:

Generalization is represented by a triangle with a line.

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Generalization is an IS_A relationship.


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Aggregation is the process of compiling information on an object, thereby abstracting a higher level object. So, an entity Person is derived by aggregating the characteristics name, house_no., city and social security number(SSN).

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Another form of aggregation says that it is abstracting a relationship between objects and viewing the relationship as an object. So, in Figure 3, the Enrollment relationship between entities student and Course entity can be viewed as entity REGISTRATION.

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In simple terms, Aggregation is a process when relation between two entities is treated as a single entity.

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