Part 7 Object DBMSs
The preceding chapters of this book concentrate on the relational model and relational
systems. The justification for this is that such systems are currently the predominant
DBMS for traditional business database applications. However, relational systems are
not without their failings, and the object-based DBMS is a major development in the
database systems area that attempts to overcome these failings. Chapters 25–28 examine
this development in some detail.
Chapter 25 acts as an introduction to object-based DBMSs and first examines the types
of advanced database applications that are emerging, and discusses the weaknesses of the
relational data model that makes it unsuitable for these types of applications. The chapter
then introduces the main concepts of object orientation. It also discusses the problems of
storing objects in a relational database.
Chapter 26 examines the object-oriented DBMS (OODBMS), and starts by providing an
introduction to object-oriented data models and persistent programming languages. The
chapter discusses the difference between the two-level storage model used by conventional
DBMSs and the single-level model used by OODBMSs, and how this affects data access.
It also discusses the various approaches to providing persistence in programming languages
and the different techniques for pointer swizzling, and examines version management,
schema evolution, and OODBMS architectures. The chapter concludes by briefly
showing how the methodology presented in Part 4 of this book may be extended for
object-oriented databases.
Chapter 27 addresses the object model proposed by the Object Data Management Group
(ODMG), which has become a de facto standard for OODBMSs. The chapter also examines
ObjectStore, a commercial OODBMS.
Chapter 28 examines the object-relational DBMS, and provides a detailed overview of
the object management features that have been added to the new release of the SQL
standard, SQL:2003. The chapter also discusses how query processing and query
optimization need to be extended to handle data type extensibility efficiently. The chapter
concludes by examining some of the object-relational features within Oracle.
The preceding chapters of this book concentrate on the relational model and relational
systems. The justification for this is that such systems are currently the predominant
DBMS for traditional business database applications. However, relational systems are
not without their failings, and the object-based DBMS is a major development in the
database systems area that attempts to overcome these failings. Chapters 25–28 examine
this development in some detail.
Chapter 25 acts as an introduction to object-based DBMSs and first examines the types
of advanced database applications that are emerging, and discusses the weaknesses of the
relational data model that makes it unsuitable for these types of applications. The chapter
then introduces the main concepts of object orientation. It also discusses the problems of
storing objects in a relational database.
Chapter 26 examines the object-oriented DBMS (OODBMS), and starts by providing an
introduction to object-oriented data models and persistent programming languages. The
chapter discusses the difference between the two-level storage model used by conventional
DBMSs and the single-level model used by OODBMSs, and how this affects data access.
It also discusses the various approaches to providing persistence in programming languages
and the different techniques for pointer swizzling, and examines version management,
schema evolution, and OODBMS architectures. The chapter concludes by briefly
showing how the methodology presented in Part 4 of this book may be extended for
object-oriented databases.
Chapter 27 addresses the object model proposed by the Object Data Management Group
(ODMG), which has become a de facto standard for OODBMSs. The chapter also examines
ObjectStore, a commercial OODBMS.
Chapter 28 examines the object-relational DBMS, and provides a detailed overview of
the object management features that have been added to the new release of the SQL
standard, SQL:2003. The chapter also discusses how query processing and query
optimization need to be extended to handle data type extensibility efficiently. The chapter
concludes by examining some of the object-relational features within Oracle.
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