1. 1 Pertemuan 5 The structure part of object data model Matakuliah: M0174/OBJECT ORIENTED DATABASE Tahun: 2005 Versi: 1/0

2. 2 Learning Outcomes Pada akhir pertemuan ini, diharapkan mahasiswa akan mampu : Mahasiswa dapat Menjelaskan struktur object data model (C2)

3. 3 Outline Materi Entities and object The identity of an object The state of an object

4. 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.

5. 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.

6. 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

7. 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

8. 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.

9. 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.

10. 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 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.

11. 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

12. 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