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Object-Database

Compare. Extend. New data. ODL, OQL. Object-Database. Challenge. Identity. Inheritance. Design. Objectives. Overview of ODMG Data Model Object Data Language – ODL Object Query Language - OQL. ODMG Data Model. Conceived by ODMG in 1991.

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Object-Database

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  1. Compare Extend New data ODL, OQL Object-Database Challenge Identity Inheritance Design

  2. Objectives • Overview of ODMG Data Model • Object Data Language – ODL • Object Query Language - OQL

  3. ODMG Data Model • Conceived by ODMG in 1991. • Provides a standard model for object databases. • Supports object definiton via ODL. • Supports object querying via OQL. • Supports a variety of data types and type constructor. • The basis for an OODBMS.

  4. Object vs Class Collection of object OBJECT CLASS Unique oid Same properties Using Object Data Language to specify properties of class.

  5. Object Data Language – ODL • ODL supports semantics constructs of OODBMS. • ODL is independent of any programming language. • ODL is used to create object specification (classes and interfaces) • ODL is not used for database manipulation.

  6. Class CLASS attributes methods relationships

  7. Class • Atrributes: atomic type or structured type. • Methods: • Functions that can be applied to objects of the class. • No analog to methods in the ER or relational models.

  8. Class • Relationships: • Type is a reference to an object or a collection such references. • Show how an object is related to one or more objects of the same class or of a different class. • Has a corresponding inverse relationship.

  9. Example showAt nowShowing

  10. Example

  11. Example

  12. Example

  13. Object Query Language - OQL • OQL is ODMG’s query language. • OQL works closely with programming languages such as C++. • Embedded OL statement return objects that are compatible with the type system of the host language. • OQL’s syntax is similar to SQL with additional features for object.

  14. Example

  15. Example

  16. Example

  17. Compare Extend New data ODL, OQL Object-Database Challenge Identity Inheritance Design

  18. RDBMS versus ORDBMS • RDBMS does not support the extensions that ORDBMS supports. • Relational system is easier to use because there are fewer features to master. • RDBMS is less versatile than an ORDBMS.

  19. OODBMS vs ORDBMSSimilarities • Both support user-defined ADTs, structired types, object type and inheritance. • Both support a query language for manipulating collection type: • ORDBMS: extended form of SQL • OODBMS: ODL/OQL. • ORDBMS add OODBMS features to an RDBMS. OODBMS have developed query language based on relational query language. • Both provide DBMS functionality.

  20. OODBMS vs ORDBMSDifferences • OODBMS try to add DBMS functionality to a programming language, whereas ORDBMS try to add richer data type ro a relational DBMS. • OODBMS aim to achieve seamless integration with a programming language, whereas it’s not an important goal for an ORDBMS.

  21. OODBMS vs ORDBMSDifferences • The query facilities of OQL are not support efficiently in most OODBMS, whereas they are the centerpiece of an ORDBMS. • OODBMS have been optimized to directly support object oriented applications and specific OO languages. ORDBMSs are supported by most of the ‘major players’ in the DBMS market place.

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