| In the case where the semigroup variety has a particular closure property with respect to programs, we are able to give precise characterizations of these regular languages. |
| In this paper we are going to follow their footsteps constructing the skew semigroup ring and prove its associativity without using approximate identity. |
| While this description of piecewise syndeticity looks somewhat forbidding, it has the advantage of making sense in any semigroup. |
| Equivalently a regular semigroup in which idempotents commute. |
| Let S be a regular semigroup with set E of idempotent elements. |
| We show that the two définitions are really différent, even under strong restrictive conditions about the algebraic structure of the semigroup. |
