Consider the constraint set C consisting of the equation x1+x2 = 2x3 and domains xj ∈ {0, 1, 2, 3, 4, 5} for j = 1, 2, 3.
Reduce the domains so as to achieve bounds completeness.
Reduce them further to achieve domain completeness.
Add to C one or more 2-variable inequalities that, together with the reduced domains, make the set 2-complete.