DB Structures - Object oriented

Developed in the 1990's Features Made up of objects that package (encapsulates) attributes and methods that operate on the objects. Include data types such as standard (integer, character, etc), documents, graphics.

Terms

• Object - structure that package (encapsulates) attributes and methods that operate on the objects.
• Encapsulation - Attributes and properties are hidden from the outside world and accessed via an interface.
• Class -Objects with the same (or similar) properties.
• Inheritance - when arranged in a hierarchy each class assumes the attributes/properties of the parent class.
• Identity - An external identifier for each object that is not accessible to and cannot be modified by an other object or application (Means there is no concept of a primary key).
• Domains - Set of all data types and ranges of values an attribute may take. Includes simple data types such as Integer, character, etc, and others like Graphics, Spatial (Graphical Information Systems), Documents, etc.
• Examples:
  • Jade (Cardinal NZ), Gemstone, Open ODB (Hewlett-Packard), Object/DB (Digital)

Ref: McFadden,F & Hoffer J (1994) Ch5.

• Historically complex data structures exist only for the moment, in primary memory and closely integrated with the application. This often means unwieldy and unnecessarily large quantities of data shipped to the client in a networked environment.
• A major influence in the emergence of object based databases is the World Wide Web, with it rich multimedia and object-oriented languages like Java.
• An object-relational database will be called on to do heterogeneous joins between object and relational data
  Example: The number of people under 21 (relational query) living within a 5 km radius of an airport (GIS-object based query)
• Two object model approaches are emerging;
  • Operate the entire database as relational, and translate the applications object-oriented instructions,
    Examples: Sybase (Object- connector), Hewlett-Packard (Odapter)
  • Incorporate special tools into the DBMS to manage object directly - or to manage particular kinds of objects.
    Examples: Informix (datablades from Illustra), Oracle (data cartridges) and Sybase (Snap-ins).
• Terms
  • Datablades (Informix)
    • Plug directly into the database kernel. They encapsulate the data type and the way of handling it (class and method in traditional oo terminology) - and identify these to the kernel by way of a metadata structure, so the DBMS knows where to look for instructions on how to manage the datatype.
  • COBRA (Common Object Request Broker Architecture)
    • A standard interface allowing for reusable object based components for databases.
  • D/COM (Distributed Component Object Model) - Microsoft
    • An interface allowing for reusable object based components for databases, from Microsoft.
  • Bell, S. (1996, Dec 16)

[Rev: 18/10/98] Sep-98 © 1998 V/2-Com (Verhaart), P O Box 8415, Havelock North, New Zealand.