Object Relational DBMSs Presented By: Sajida Hayek

Outline Why ORDBMS? What is ORDBMS? Stonebreaker’s view Advantages and disadvantages of ORDBMS Object-Relational Operations Object-Relational Mapping

Why ORDBMS

What is ORDBMS? Systems that attempt to extend relational database systems with the functionality necessary to support a broader class of applications and, in many ways, provide a bridge between the relational and object-oriented paradigms.

Stonebraker’s View

Advantages of ORDBMSs Resolves many of known weaknesses of RDBMS. Reuse and sharing Preserves significant body of knowledge and experience gone into developing relational applications.

Disadvantages of ORDBMSs Complexity. Increased costs. Simplicity and purity of relational model are lost.

Object-Relational Operations: CRUD Common OR operations: Create - save (persist) a new object in the database Retrieve an object from the database Update data for an object already saved in database Delete object's data from the database

Object-Relational Mapping (ORM) A software system that shuttles data back and forth between database rows and objects Appears as a normal database user to the database Can share the database and tables with other apps Object-intensive app Database Other apps ORM

Object-Relational Mapping Cont. Map between an object and a row in a database table. Location id: int name: String address: String Class should have an identifier attribute Data Mapper convert object to table row data, convert data types, instantiates objects Data Mapper LOCATIONS PK id INTEGER name VARCHAR(80) address VARCHAR(160) Database Table identifier is usually the primary key of table

Mapping an Object ku : Location id = 101 name = "Kasetsart University" address = "90 Pahonyotin ..." object diagram save( ) LOCATIONS id name address 101 Kasetsart University 90 Pahonyotin ... 102 Seacon Square 120 Srinakarin ...

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