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Pertemuan 2Overview of data model

Matakuliah : M0174/OBJECT ORIENTED DATABASE

Tahun : 2005

Versi : 1/0

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Learning Outcomes

Pada akhir pertemuan ini, diharapkan mahasiswa

akan mampu :

• Mahasiswa dapat Menjelaskan konsep tentang object data model (C2)

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Outline Materi

• Object Data models

• A brief history of data models

• First generation database technology

• Second generation database technology

• Third generation database technology

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Object Data models

• What is the object data models ?

• A data model has two important roles– It is the basis for DBMSs– It may be used to describe and analyse

database system

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A brief history of data models

• 1950s assembler language and machine code

• 1960s COBOL and FORTRAN

• Database technology has continued to evolve, in response to a need for more sophisticated ways of managing, administering, and using data

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A brief history of data models

• The first two generations of data models were concerned mainly with representing the meaning of data in terms of the structure of the information represented.

• The third generation of data models, which includes the object data model, in addition represented the meaning of data in terms of the behavior associated with the information system.

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First generation database technology

– The first of database technology was based upon network data model and the hierarchical data model.

– In this model information is represented as collections of interlinked record.

– The hierarchical model allows records to be linked to form tree structure and the network model allows records to be linked into network structure

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First generation database technology

Customer

Sales Order Sales Order

Product

Sales Order Sales Order

Hierarchical Model Network Model

Customer

Sales Order Sales Order

Product

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First generation database technology

• The First Generation Data Model Limitation– There is no clean separation between the logical

structure of the data and the way in which it is physically implemented. Consequentially the interface between programs and DBMS is complicated and a knowledge of how the link record are implemented often has to be written into the programs.

– The database languages manipulate only one record at a time.

– There is no theoretical foundation for hierarchical and network data model

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Second generation database technology

• The second generation of database technology is based upon the relational data model.

• The relational model represent all information as table of data values.

• A table is used represent some type of real world entity, or type of relationship entity, and the row represent occurrences of the entity or relationships

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Second generation database technology

• A strength of the relational model is that it has a precise mathematical definition, and therefore provide a theoretical model for database system.

• A table in a relational database is, in fact a representation of a mathematical relation, and operates which manipulate the tables are base upon the corresponding mathematical operation upon relation.

• In particular, the relation model includes an algebra for manipulating the table, which provide basis for new generation of database language epitomized by SQL.

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Second generation database technology

• The Attractions of The Relational Models– Mathematical Rigour – Simplicity. All information is represented in the

relational model using one simple logical structure, the table

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Second generation database technology

• Second Generation Data Model Limitation– Tabular presentation is inappropriate for representing

the complex structure which exist in the real world. – Behavioral limitation: Relational database language

express only a small subset of the ways in which data can be manipulated. In order to define complex computation upon data it is necessary to use other programming language.

– Relational model supports only structural semantic, not behavior semantics.

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Third generation database technology

• There are two dominant third generation data models:– Object Relational Data Model (ORDM)– Object Oriented Data Model (OODM)

• ORDM are evolutionary approach, since the adapt and enhance the relational model.

• Extensions to the relational model have been defined to allow direct modeling of complex structure, e.g, by allowing table to be nested and by extensions to relational algebra to increase its expressive power

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Third generation database technology

• Object Oriented Data Model are more expressive than those of the previous generations. They provide a richer representation of the structure of the information represented by the data than is possible using first or second generation models. Also they provide facilities for representing within the database behavior of the information represented by the data

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SUMMARY

• The Evolution of Data Models

Application Program

Data Files

File SystemApplication Program

Structural semantic

Data Files

Database System

Application Program

Behavior Semantic

Structural Semantic

Data Files

Object Database System