A relational database management system, based on the principles laid down in the book "Databases, Types, and The Relational Model: The Third Manifesto" by C. J. Date and Hugh Darwen.
Sedna is a native full-featured XML database management system.
Sedna is a free native XML database which provides a full range of core database services - persistent storage, ACID transactions, security, indices, hot backup. Flexible XML processing facilities include W3C XQuery implementation, tight integration of XQuery with full-text search facilities and a node-level update language.
DBIO is a tool to simulate Online Transaction Processing Database, which can be used to model production envirment for I/O test. A standard configuration file contained in the software simulates TPCC-Like I/O workload, which is modeled from DB2 Database running TPCC-Like workload. DBIO can also do data consistency check after the I/O workload test.
picoSQL is an Italian multi-user relational database management system with transactions support. Because it derives from a commercial project, it is already robust, fast, and rather complete.