Object–relational database

However, a more popular alternative for achieving such a bridge is to use a standard relational database systems with some form of object–relational mapping (ORM) software.

Whereas traditional RDBMS or SQL-DBMS products focused on the efficient management of data drawn from a limited set of data-types (defined by the relevant language standards), an object–relational DBMS allows software developers to integrate their own types and the methods that apply to them into the DBMS.

Complex data creation in most SQL ORDBMSs is based on preliminary schema definition via the user-defined type (UDT).

Encapsulation in OOP is a visibility degree declared, for example, through the public, private and protected access modifiers.

The researchers aimed to retain a declarative query-language based on predicate calculus as a central component of the architecture.

By the next decade, PostgreSQL had become a commercially viable database, and is the basis for several current products that maintain its ORDBMS features.

For example, IBM Db2, Oracle Database, and Microsoft SQL Server, make claims to support this technology and do so with varying degrees of success.

Using a traditional RDBMS, collecting information for both the user and their address requires a "join": The same query in an object–relational database appears more simply: