... installation optimised for a certain kind of DB;
2. be a stack of core black boxes to provide general DBMS functionality, plus a range of plug-in black boxes to support different physical storage mechanisms & scalar data types;
3. employ code designed with a mixture of functional, OO & other methods so as to minimise internal DBMS state complexity.
The 'Northumbria Website' (above RHS menu option) describes the vision, specification & design of the RAQUEL language & DBMS architecture.