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Pertemuan 25Object Relational Database Management

System

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 Menghasilkan rancangan database objek (C3)

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Outline Materi

• Limitations of the second generation databases

• The nested relational data model

• Object relational data models

• SQL3

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Limitations of the second generation databases

• The main strengths of the Relational Data model are :– Simplicity

• All information is visible as values in tables

– Rigour• The relational data model has been defined with

theoretical rigour and provides a mathematical basis for researching issue such as database design, database language, and query optimisations

– Practicality and generality

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Limitations of the second generation databases

• In summary, the rules are:– All information must be represented as values

in tables– Each data item must be accessible by the

combination of table name, key value, and column name

– The RDBMS must support null values for representing missing or inapplicable information a systematic way

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Limitations of the second generation databases

– The database description (the schema) must be represented at the logical level as values in tables

– At least one relational database language should be expressible as strings of characters and have a well defined syntaxs

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The nested relational data model

• Nested Relational Data Model represent a data model which developed to close over lacking of relational data model in order to defining entities which complex.

• The nested relational data model remove the constraint that tables are flat.

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The nested relational data model

• In the nested relational data model, the values stored in tables can also be tables.

• The nested relational data model can be viewed as a step towards an object relational data model.

• NRDM table can be used to represent hierarchically structured entities. (this was also possible using the first generation) But NRDM also provides the strength of theoretical basis with its algebra

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The nested relational data model

• Example

Employee Number

E1

E2

Projects

Project_ Number hours

P1

P4

P1

10

5

20

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Object relational data models

• There are two general approaches towards third generation database technologies with integrate object-oriented features:Object Database – this extend object modelObject Relational Database – this extend the

relational data model to include data modeling features typically associated with object oriented system.

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Object relational data models

• In late 1980s, object & object relational database were seen as rivals, rather than complementary technologies.

• The respective visions of what the third generation database technology should be like were published by groups of leading researchers as “manifesto” documents – “the object oriented database manifesto” & “the third generation database manifesto”.

• The third generation database manifesto sees them as a means of extending a core relational data model

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SQL3

• SQL3 specification extends SQL to provide object oriented features but remains upwardly compatible with previous SQL standards. This feature include:Abstract Data Type (ADT)Generalization & Specialization hierarchiesAssertions & Triggers

• SQL3 provides two way to model entities as row and as ADT

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SUMMARY

• Object relational database extend the relational data model to address its weaknesses.

• In particular, object relational database have been developed to represent entities with complex structures & behavior such as exist in many scientific application, multimedia & GIS

• The main strengths of the Relational Data model are :– Simplicity– Rigour– Practicality and generality