Unambiguous Tree Languages Are Topologically Harder Than Deterministic Ones

@inproceedings{Hummel2012UnambiguousTL,
  title={Unambiguous Tree Languages Are Topologically Harder Than Deterministic Ones},
  author={Szczepan Hummel},
  booktitle={GandALF},
  year={2012}
}
  • S. Hummel
  • Published in GandALF 7 October 2012
  • Computer Science
The paper gives an example of a tree language G that is recognised by an unambiguous parity automaton and is analytic-complete as a set in Cantor space. This already shows that the unambiguous languages are topologically more complex than the deterministic ones, that are all coanalytic. Using set G as a building block we construct an unambiguous language that is topologically harder than any countable boolean combination of analytic and coanalytic sets. In particular the language is harder… 

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