REFLEXIVE RELATIONS, EXTENSIVE TRANSFORMATIONS AND PIECEWISE TESTABLE LANGUAGES OF A GIVEN HEIGHT
Abstract
Straubing deduced from Simon's theorem that monoids of reflexive relations as well as monoids of order preserving extensive transformations generate the pseudovariety of -trivial monoids. We refine these results by showing that each pseudovariety in Simon's hierarchy of
-trivial monoids is generated by a single relation/transformation monoid. From this and from some results by Blanchet–Sadri we obtain a complete solution of the finite basis problem for Straubing's monoids.
Dedicated to John Rhodes on the occasion of his 65th birthday