Generic Results for Concatenation Hierarchies

Concatenation Hierarchies and Forbidden Patterns

We make the following progress on the dot–depth problem: (1) We introduce classes CB n and CL n of starfree languages defined via forbidden patterns in finite automata. It is shown for all n 0 that CB n (CL n) contains level n + 1=2 of the dot–depth hierarchy (Straubing–Thérien hierarchy, resp.). Since we prove that CB n and CL n have decidable membership problems, this yields a lower bound alg...

Concatenation Hierarchies: New Bottle, Old Wine

We survey progress made in the understanding of concatenation hierarchies of regular languages during the last decades. This paper is an extended abstract meant to serve as a precursor of a forthcoming

Forbidden-patterns and word extensions for concatenation hierarchies

The forbidden pattern approach to concatenation hierarchies

Arbres et Hierarchies de Concatenation