Lecture Database system concepts - Chapter 9: Object­ based databases

The object-relational model, described in chapter 9, combines features of the re-lational and object-oriented models. This model provides the rich type system of object-oriented databases, combined with relations as the basis for storage of data. It applies inheritance to relations, not just to types. The object-relational data model provides a smooth migration path from relational databases, which is attractive to relational database vendors. | Chapter 9: Object­Based Databases Database System Concepts ©Silberschatz, Korth and Sudarshan See ­ for conditions on re­use Database System Concepts ©Silberschatz, Korth and Sudarshan Chapter 9: Object­Based Databases s Complex Data Types and Object Orientation s Structured Data Types and Inheritance in SQL s Table Inheritance s Array and Multiset Types in SQL s Object Identity and Reference Types in SQL s Implementing O­R Features s Persistent Programming Languages s Comparison of Object­Oriented and Object­Relational Databases Database System Concepts ­ 5th Edition, Aug 9, 2005. 9. ©Silberschatz, Korth and Sudarshan Object­Relational Data Models s Extend the relational data model by including object orientation and constructs to deal with added data types. s Allow attributes of tuples to have complex types, including non­atomic values such as nested relations. s Preserve relational foundations, in particular the declarative access to data, while extending modeling power. s Upward compatibility with existing relational languages. Database System Concepts ­ 5th Edition, Aug 9, 2005. 9. ©Silberschatz, Korth and Sudarshan Complex Data Types s Motivation: q q q Permit non­atomic domains (atomic ≡ indivisible) Example of non­atomic domain: set of integers,or set of tuples Allows more intuitive modeling for applications with complex data s Intuitive definition: q allow relations whenever we allow atomic (scalar) values — relations within relations q Retains mathematical foundation of relational model q Violates first normal form. Database System Concepts ­ 5th Edition, Aug 9, 2005. 9. ©Silberschatz, Korth and Sudarshan Example of a Nested Relation s Example: library information system s Each book has q title, q a set of authors, q Publisher, and q a set of keywords s .