Pertemuan 25 Object Relational Database Management System

1. Pertemuan 25Object Relational Database Management System Matakuliah : M0174/OBJECT ORIENTED DATABASE Tahun : 2005 Versi : 1/0

2. Learning Outcomes Pada akhir pertemuan ini, diharapkan mahasiswa akan mampu : • Mahasiswa dapat Menghasilkan rancangan database objek (C3)

3. Outline Materi • Limitations of the second generation databases • The nested relational data model • Object relational data models • SQL3

4. 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

5. 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

6. 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

7. 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.

8. 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

9. The nested relational data model • Example Employee Number Projects Project_ Number hours E1 P1 P4 10 5 E2 P1 20

10. Object relational data models • There are two general approaches towards third generation database technologies with integrate object-oriented features: • Object Database – this extend object model • Object Relational Database – this extend the relational data model to include data modeling features typically associated with object oriented system.

11. 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

12. 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 hierarchies • Assertions & Triggers • SQL3 provides two way to model entities as row and as ADT

13. 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