Facing the demand to support more complex data representations, the relational model’s main vendors evolved the model further and created the extended relational data model (ERDM). The ERDM adds many of the OO model’s features within the inherently simpler relational database structure. The ERDM gave birth to a new generation of relational databases supporting OO features such as objects (encapsulated data and methods), extensible data types based on classes, and inheritance. That’s why a DBMS based on the ERDM is often described as an object/relational database management system (O/R DBMS)
The use of complex objects received a boost with the Internet revolution. When organizations integrated their business models with the Internet, they realized the potential of the Internet to access, distribute, and exchange critical business information.
This resulted in the widespread adoption of the Internet as a business communication tool. It is in this environment that Extensible Markup Language (XML) emerged as the de facto standard for the efficient and effective exchange of structured, semistructured, and unstructured data.
Organizations using XML data soon realized there was a need to manage the large amounts of unstructured data such as word-processing documents, Web pages, e-mails, diagrams, etc., found in most of today’s organizations. To address this need, XML databases emerged to manage unstructured data within a native XML format , Database Connectivity and Web Technologies, for more information about XML). At the same time, O/R DBMSs added support for XML-based documents within their relational data structure.