Two algebraic approaches to variants of the concatenation product

Abstract

We extend an existing approach of the bideterministic concatenation product of languages aiming at the study of three other variants: unambiguous, left deterministic and right deterministic. Such an approach is based on monoid expansions. The proofs are purely algebraic and use another approach, based on properties on the kernel category of a monoid relational morphism, without going through the languages. This gives a unified fashion to deal with all these variants and allows us to better understand the connections between these two approaches. Finally, we show that local finiteness of an M -variety is transferred to the M -varieties corresponding to these variants and apply the general results to the M -variety of idempotent and commutative monoids.