Matakuliah
Tahun
Versi
: M0174/OBJECT ORIENTED DATABASE
: 2005
: 1/0
Pertemuan 5
The structure part of object data
model
1
Learning Outcomes
Pada akhir pertemuan ini, diharapkan mahasiswa
akan mampu :
• Mahasiswa dapat Menjelaskan struktur
object data model (C2)
2
Outline Materi
• Entities and object
• The identity of an object
• The state of an object
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Entities and object
• An object database contains a collection of
object, each of which represents one of
the entities that are of interest to the
organization that the object database
serves.
• Entities are things about which we wish to
record facts and which are distinguishable,
one from other.
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Entities and object
• Each object has following structure in
order to represent the characteristic of an
entity:
– Identity: a unique and unalterable object
identifier assigned to the object.
– State: the state of an object is the set of
values that it contains. The values represent
fact about the entities represented by the
object.
– Behavior: the behavior of an object is the set
of operations that can be applied to it.
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Entities and object
• Mutable & Literals Object
– Mutable object is an object which can change
its own state.
– Literal object is an object which cannot
change its own state.
– A literal is a container for a fixed value and
serves the same purpose as a constant in
programming language
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Entities and object
– Mutable object is a container for fact about an
entities, the properties of which may change
over time.
– The literal object is therefore a sensible
restriction, since the represented values will
not change. A consequence is that the state of
a literal also act as its object identifier
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The identity of an object
• An object identifier is an automatically
assigned and unchangeable value that
uniquely identifies that object and
distinguishes it from all other object.
• The object identifier is separate from the
object state and it provides a means of
referencing object within the system.
• Hence object identifier can be used to
represent association between objects.
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The state of an object
• An object state can be thought of as the
set of values that the object contains.
Each value represent property of the entity
represented by the object.
• An object state can carry two types of
property:
– Attributes: Value which represent fact about
entity represented by that object.
– Relationships: value which represent
association with other object.
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The state of an object
• The Behavior of an Object
– Object behavior define by set of operations.
This operations define all the things that can
be done to that object and therefore define
the object’s interface.
– In general, there are two types of operation:
• Update Operations: which modify the state of an
object.
• Retrieval Operations: which query the state of an
object.
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SUMMARY
• All entities are represented as object
• Each object has an identity, state, and
behaviour
• Values are represented by objects which
cannot change their state, called literals
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SUMMARY
• Other entities are represented by mutable
objects which can change their state
• The integration of state and behaviour
within an objects is called encapsulation
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