Example: EMPLOYEE entity refers to: The attributes and relationships of each We say that an entity that is a member of a subclass inherits all the attributes of
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A class hierarchy provides an inheritance mechanism which allows a class to inherit properties (attributes and methods) from its superclasses In single inheritance systems, a class can have at most one direct superclass and therefore can only inherit from that superclass The class hierarchy forms a tree
oodbms.concepts
shorter times with the added facilities of an available relational DBMS (i e , transaction In the other case [B090], attribute inheritance was implemented on top
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Subclasses, superclasses, and inheritance • Specialization inheritance • A subclass inherits all attributes of its superclass – Example: • Employee has a
Dr.Osama Part Enhanced Entity Relationship Diagram (EER)
attribute and relationship inheritance Example: EMPLOYEE may be further grouped into: Example: Another specialization of EMPLOYEE based on
ch Enhanced Entity Relationship (EER) Modeling
attribute and relationship inheritance • superclass / subclass relationship • example: SECRETARY, ENGINEER, MANAGER, -> a subset of the entities that
object-relational database management system (ORDBMS) to overcome relational and have that type inherit existing attributes from employee_ty [11]
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Partially automated techniques to map to logical (DBMS dependent) model Attribute Inheritance: subclasses inherit all the attributes of the superclass
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Specific relationship types ▫ Subclass can be a subclass wrt more than one superclass ▫ Type inheritance • Subclass entity has all attributes and participates
EER Model
Subclasses, Superclasses, and Inheritance • Specialization Example of Other Notation: Representing Subclass entity inherits all attributes and relationships
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A class hierarchy provides an inheritance mechanism which allows a class to inherit properties (attributes and methods) from its superclasses. • In single
?1) When using attribute inheritance can reduce the use of nulls in a single entity relation (that contains multiple subclasses).
Problem of Multiple Inheritance. • Inherit Attributes methods from: • Both/ALL superclasses. • Only dominant superclass (all cases or only where conflict).
attribute and relationship inheritance Attribute Inheritance in Superclass /. Subclass Relationships. An entity that is member of a subclass inherits.
Specialization/generalization. • Associated with special types of entities known as superclasses and subclasses and the process of attribute inheritance.
Generally most relationship sets in a database system are binary. Attribute inheritance – a lower-level entity set inherits all the.
is the union of objects of different entity types. • Concepts is the important mechanism of attribute and relationship inheritance. • Diagrammatic technique for
Multiple inheritance occurs when a certain subtype T is a subtype of two (or more) types and hence inherits the functions (attributes and methods) of both
INF3100/INF4100 – Database Systems OO concepts and OO-DBMS properties ... Sub-types INHERIT properties (attributes and operations) from super-types.
Object-Oriented DBMS Concepts