This work describes a novel implementation of a deductive database system which fills some gaps other systems do not. In fact, this system was born to this end and since its inception, many new features have been added (null values, outer joins, aggregates, ...). In particular, it embodies both Datalog and SQL query languages, where the same database can be queried. It enjoys an actual interactive environment for any platform (Windows, Linux, Macintosh, ...) and it has been plugged to a Java GUI IDE for easing user interaction (syntax highlighting, projects, ...). The system is distributed under GPL license, hosted by sourceforge, and heavily used all around the world.
['Fernando Sáenz-Pérez']
DES: A Deductive Database System