R. Khosravi - Department of Mathematics, Fasa University, P.O.Box ۷۴۶۱۷-۸۱۱۸۹, Fasa, Iran.

In this paper the notion of Rees short exact sequence for S-posets is introduced, and we investigate the conditions for which these sequences are left or right split. Unlike the case for S-acts, being right split does not imply left split. Furthermore, we present equivalent conditions of a right S-poset P for the functor Hom(P;-) to be exact.

S-posets, pomonoids, Rees short exact sequence, projective