Source : Free On-Line Dictionary of Computing

domain calculus
     
         A form of {relational calculus} in which {scalar}
        variables take values drawn from a given {domain}.
     
        Examples of the domain calculus are {ILL}, {FQL}, {DEDUCE} and
        the well known {Query By Example} (QBE).  {INGRES} is a
        {relational DBMS} whose {DML} is based on the relational
        calculus.