A characterization of regular expressions under bisimulation

@article{Baeten2007ACO,
  title={A characterization of regular expressions under bisimulation},
  author={Jos C. M. Baeten and Flavio Corradini and Clemens Grabmayer},
  journal={J. ACM},
  year={2007},
  volume={54},
  pages={6}
}
We solve an open question of Milner [1984]. We define a set of so-called well-behaved finite automata that, modulo bisimulation equivalence, corresponds exactly to the set of regular expressions, and we show how to determine whether a given finite automaton is in this set. As an application, we consider the star height problem.