String-rewriting systems
On the regularity of languages on a binary alphabet generated by copying systems
Information Processing Letters
Algebraic Theory of Automata & Languages
Algebraic Theory of Automata & Languages
Deleting string rewriting systems preserve regularity
Theoretical Computer Science - Developments in language theory
Languages generated by iterated idempotency
Theoretical Computer Science
Closure of language classes under bounded duplication
DLT'06 Proceedings of the 10th international conference on Developments in Language Theory
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When using string-rewriting systems in the context of formal languages, one of the most common questions is whether they preserve regularity. A class of string-rewriting systems that has received attention lately are idempotency relations. They were mainly used to generate languages starting from a single word.Here we apply these relations to entire languages and investigate whether they preserve regularity. For this, it turns out to be convenient to define two more general classes of string-rewriting systems, the k-period expanding and the k-period reducing ones. We show that both preserve regularity. This implies regularity preservation for many classes of idempotency relations.