Dbms-Enhanced Entity-Relationship Modeling C12

Front 1

Superclass

Back 1

An entity type that includes one or more distinct subgroupings of its occurrences.

Front 2

Subclass

Back 2

A distinct subgrouping of occurrences of an entity type.

Front 3

Characterization of Super/Sub Classes

Back 3

Superclass/subclass relationship is one-to-one (1:1).

Superclass may contain overlapping or distinct subclasses.

Not all members of a superclass need be a member of a subclass.

Front 4

Attribute Inheritance

Back 4

An entity in a subclass represents same ‘real world’ object as in superclass, and may possess subclass-specific attributes, as well as those associated with the superclass.

Front 5

Specialization

Back 5

Process of maximizing differences between members of an entity by identifying their distinguishing characteristics.

Front 6

Generalization

Back 6

Process of minimizing differences between entities by identifying their common characteristics.

Front 7

Two constraints that may apply to a specialization/generalization:

Back 7

-participation constraints
-disjoint constraints.

Front 8

Participation constraint

Back 8

Determines whether every member in superclass must participate as a member of a subclass.
May be mandatory or optional.

Front 9

Disjoint constraint

Back 9

Describes relationship between members of the subclasses and indicates whether member of a superclass can be a member of one, or more than one, subclass.
May be disjoint or nondisjoint.

Front 10

There are four categories of constraints of specialization and generalization:

Back 10

-mandatory and disjoint
-optional and disjoint
-mandatory and nondisjoint
-optional and nondisjoint.