  A first order inference system, called R-calculus, is defined to develop the
specifications. It is used to eliminate the laws which is not consistent with
the user's requirements. The R-calculus consists of the structural rules, an
axiom, a cut rule, and the rules for logical connectives. Some examples are
given to demonstrate the usage of the R-calculus. The properties about
reachability and completeness of the R-calculus are formally defined and are
proved.
