1 Pertemuan 5 The structure part of object data model
Matakuliah: M0174/OBJECT ORIENTED DATABASE Tahun: 2005 Versi:
1/0
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2 Learning Outcomes Pada akhir pertemuan ini, diharapkan
mahasiswa akan mampu : Mahasiswa dapat Menjelaskan struktur object
data model (C2)
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3 Outline Materi Entities and object The identity of an object
The state of an object
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4 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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5 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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6 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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7 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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8 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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9 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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10 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
objects 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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11 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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12 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