Berkeley DB XML is an application-specific native XML data manager
built on Berkeley DB, the world's most widely deployed data management
engine.  Berkeley DB XML provides fast, reliable, scalable and
cost-effective storage and retrieval for native XML data and
semi-structured data.

Berkeley DB XML is supplied as a library that links directly into the
application's address space.  This provides superior performance by
eliminating bottlenecks that occur in client-server systems.