Suppose you want to define a predicate named date/1, which conflicts with the ECLiPSe builtin called date/1. In this case the compiler will produce one of the following messages
warning: redefining a system predicate in date / 1 *** trying to redefine a procedure with another type: date / 1depending on whether the definition or a call to the predicate was encountered first by the compiler. Both can be avoided by declaring the predicate as local. This declaration must be given before the first call to the predicate:
:- local date/1. p(Y) :- date(Y). date(1999).Note that the date/1 builtin is now hidden by your own definition, but only in the module where you have redefined it
.
In all other modules, the builtin is still visible.
The same holds for the redefinition of protected predicates,
see also section 
and appendix .