WEBexist. More precisely, Ris a logical relation of semigroups if it satisfies the requirement: x R x0∧y R y0 =⇒xy R x0y0 (1.1) That is, the multiplication operations of the two semigroups are related by R×R→R. A logical relation of monoids respects, in addition, the unit, i.e., the two units are related by R. A logical