Jean Berstel Transductions and Context - Free Languages

Context - Free Languages and

Context - Free Languages and PushdownAutomataJean -

Relational morphisms, transductions and operations on languages

The aim of the article is to present two algebraic tools (the representable transductions and the relational morphisms) that have been used in the past decade to study operations on recognizable languages. This study reserves a few surprises. Indeed, both concepts were originally introduced for other purposes : representable transductions are a formalization of automata with output and have bee...

Operations Preserving Recognizable Languages

Given a subset S of N, filtering a word a0a1 · · · an by S consists in deleting the letters ai such that i is not in S. By a natural generalization, denote by L[S], where L is a language, the set of all words of L filtered by S. The filtering problem is to characterize the filters S such that, for every recognizable language L, L[S] is recognizable. In this paper, the filtering problem is solve...

Operations preserving regular languages

Given a strictly increasing sequence s of non-negative integers, filtering a word a0a1 · · · an by s consists in deleting the letters ai such that i is not in the set {s0, s1, . . .}. By a natural generalization, denote by L[s], where L is a language, the set of all words of L filtered by s. The filtering problem is to characterize the filters s such that, for every regular language L, L[s] is ...