Relational and object relational databases

Relational database management systems are one of the most widely-used DBMSs in the world. It is highly unlikely that any organization, institution, or personal computer today does not have or use a piece of software that rely on RBDMS.
Software applications can use relational databases via dedicated database servers or via lightweight RDBMS engines, embedded in the software applications as shared libraries.
The capabilities of a relational database management system vary from one vendor to another, but most of them adhere to the ANSI SQL standards. A relational database is formally described by relational algebra, and is based on the relational model. Object-relational database (ORD) are similar to relational databases. They support the following object-oriented model concepts:

• User-defined and complex data types
• Inheritance