ODB-II provides all the standard features you would expect to find in an object database, including the following:
A type hierarchy with inheritance (for example, the type Employee can be defined as a subtype of Person, and thereby inherits attributes such as name and address).
Polymorphism, for example, an operation to calculate the area of a shape can use different calculations according to the type of shape.
Support for complex objects, that is, for multi-valued attributes, sets and lists, and arbitrary relationships between objects.
The ability to associate operations with objects, so that the application need not be concerned with the detailed representation of an object.
A database programming language: that is, a language that combines the algorithmic power of a programming language with the query capabilities of SQL. The database programming language in ODB-II is called ODQL. It can be regarded as an integration of the syntax and functionality of C++ and SQL into a single unified fourth-generation language, which will be assimilated easily by programmers who are familiar with SQL, C or C++.
Support for transactions, locking, concurrency control, and recovery.
Tools to support the application developer, the database administrator, and the information user.
Additional features in ODB-II that are often missing from other object databases include:
The ability to add new data types, operations, and properties during use, without the need to recompile the application completely or to reorganize the database.
Facilities to access data either by navigation (following relationships between objects) or by associative query (finding data by content). The ability to find any object based on its attributes and relationships, regardless of whether an appropriate access path has been predefined.
A library of built-in classes to handle multimedia objects such as images.
The ability to write methods that access data held in external relational databases or files as if it were held within the ODB-II database.
Leading Edge Features of ODB-II
Object Database Query Language
Current Implementations of ODB-II