A Tentative Approach for the Wadge-Wagner Hierarchy of Regular Tree Languages of Index [0, 2] [chapter]

Jacques Duparc, Kevin Fournier
2015 Lecture Notes in Computer Science  
We provide a hierarchy of tree languages recognised by nondeterministic parity tree automata with priorities in {0, 1, 2}, whose length exceeds the first fixed point of the ε operation (that itself enumerates the fixed points of x → ω x ). We conjecture that, up to Wadge equivalence, it exhibits all regular tree languages of index [0, 2]. 1 We emphasize that this is done without any determinacy principle. In particular, we do not require ∆ 1 2 -determinacy. 2 not to be mistaken with an ε-move.
doi:10.1007/978-3-319-19225-3_7 fatcat:z6d2m2dhorgfzfxx2c2sx2v2si