Duro - a relational database management system
Edit by : Duro is a Relational open-source database management system. It is 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.

Duro is published under the terms of the GNU General Public License.
Current Release

The current release of Duro is 0.14, released 2009-Mar-06. Some features:

* Tuples and tables (relvars).
* Relational algebra: RENAME, select (restrict), project, EXTEND, JOIN, SEMIJOIN, UNION, Intersect, MINUS, SEMIMINUS, SUMMARIZE PER, DIVIDEBY PER, WRAP, UnWrap, GROUP, and UNGROUP.
* Virtual tables (views).
* Locking and nested transactions.
* Duro tables are true sets -- uniqueness of tuples (rows) is always enforced. When creating real tables, at least one candidate key must be supplied. A candidate key may be empty.
* User-defined types (including type constraints) and operators.
* Declarative integrity.
* Tcl interface, including support for relational expressions in Tutorial D syntax and operators implemented in Tcl (stored procedures).
* Simple GUI admin tool.
* Interpreter for the Tutorial D language. you can free download rhartmann Duro 0.14 now.