domain — the set of relations operations:  - unary: select, project - join: cartesian product, theta-join, natural join - set operations: union, intersection, difference - others: division
a set of mathematical principles that form the basis for manipulating relational table; the eight main funcitons are select, project, join, intersect, union, difference, product, and divide.
the relational algebra is a procedural language • select • project • cross product (join) • set union • set difference • rename