Super types and Subtypes

• An entity can be divided into serval subgroups or subtypes
• An entity type that can be divided into subtypes is called super type.
• A subtype is a subset ofasuper type that shares common attributes.
• Subtypes behave in exactly the same way as any other entity type.

• The primary keys of super type and subtypes are always identical

• For example an entity CUSTOMER has the attribute Customer ID,Address and Phone.

• A CUSTOMER can be an INIDIVUAL or ORGANIZATION.

Generalization

• Generalization is a process of identifying more general entity type.

• For Example Human is a more general entity type than Student and Teacher > The entity type HUMAN contains attributes that are more general than other two entity type

• It may contain the attribute like NAME, ADDRESS

• The entity type STUDENT contains the attributes which are specifies to students like ROLLNO, MARKS CLASS

Examples

Fruits →Apple. Orange, Mango Auto

Specialization

• Specialization is a process of identifying more specifies entity types

• For Example Student and Teacher are more specific entity type than HUMAN