"Rel is a project to develop a true relational database server based on a relational language called "Tutorial D". Rel is not SQL!"
"In The Third Manifesto, Date and Darwen propose a database language that:
* Is truly relational;
* Provides certain desirable programming language features, including some that are typically (but not exclusively) found under the "Object Oriented" heading;
* Represents a "firm foundation for the future of data.""
They haven't finished implementing TCLOSE (transitive closure) yet though.