摘要
SEMIGROUP S is said to be rpp (dually, lpp) if every principal right ideal aS^1(S^1a) of S, re-garded as a right (left)S^1-system, is projective. The semigroup which is both rpp and lpp is said to be abundant. These kinds of generalized regular semigroups have aroused wideattention. The Green’s,relations (~*-Green’s relations introduced by Pastijn) have formed avery useful tool in study on regular (abundant) semigroups. In order to develop the study onrpp semigroups a step further, we introduced the so-called (1)-Green’s,relation which
