Matakuliah
Tahun
Versi
: M0174/OBJECT ORIENTED DATABASE
: 2005
: 1/0
Pertemuan 3
Overview of data model (Lanjutan)
1
Learning Outcomes
Pada akhir pertemuan ini, diharapkan mahasiswa
akan mampu :
• Mahasiswa dapat Menjelaskan konsep
tentang object data model Lanjutan (C2)
2
Outline Materi
•
•
•
•
Entities and objects
Type and classes
Object identity
Inheritance
3
Entities and objects
• What are definitions :
– entities
– objects
– State
– Behaviour
– Interface
– Encapsulation
• Examples
4
Entities and objects
• Object diagram
I’m Indra
Employee
Employee_number = I01
Employee_name = ‘Indra’
Date_of_Birth = 01012000
Entity
5
Entities and objects
• The state of an object represents the
properties of the entity modeled by the
object.
• There are two types of property that can
be represented
– Attributes
– Relationships
6
Type and classes
• What are definitions :
– Object type
– Instances
– Extent
– Type
– Methods
– Implementation class
– Simply a class
7
Type and classes
• An objects is organised into three parts
– Its state
– Its interface
– The implementation
8
Object identity
• Objects can be combined to model entities
with complex structures
• Objects composed from other objects are
called complex objects
• Examples
9
Inheritance
• Objects in an object database can be
instances of many types simultaneously
• Subtype
• Supertype
• Examples
10
Inheritance
• A Subtype/Supertype relationship signifies the
following:
– An object subtype automatically inherit all of the
attributes, relationships and operations of the object
types which are its supertypes.
– An object subtype can have additional characteristic.
– An object subtype can refine the characteristics it
inherits from its supertype by redefining them.
– An object is defined on a class but is also an instance
of each of its supertypes.
– An object is amember of the extent of the type upon
which it is defined, and of the extents od each of its
supertype
11
Inheritance
• Extends works in a similar way to
subtype/supertype relationships, but with
the restriction that it relates only classes
and supports only single inheritance.
12
SUMMARY
• The object data model is a data model
• Three are now three generations of data
model :
– The network and hierarchical data models
– The relational model
– Object relational and object models
13
SUMMARY
• An object has a state and behaviour
• Objects with the same state and behaviour
characteristics are defined by an object
type
• An object is an instance of its types
• The set of instances of a type is a called
the type’s extent
14