|When Is a Bottom-up Deterministic Tree Transducer Top-down Deterministic?|
du groupe Séminaire Méthodes Formelles
|Date|| 2020-06-30 14:00-15:00|
|Titre||When Is a Bottom-up Deterministic Tree Transducer Top-down Deterministic? |
|Résumé||We consider two natural subclasses of deterministic top-down tree-to-tree transducers, namely, linear and uniform-copying transducers. For both classes we show that it is decidable whether the translation of a transducer with look-ahead can be realized by a transducer from the same class without look-ahead.
The transducers constructed in this way, may still make use of inspection, i.e., have an additional top-down deterministic tree automaton restricting the domain. We provide a second procedure which decides whether inspection can be removed and if so, constructs an equivalent transducer without inspection.
The construction relies on a precise abstract interpretation of inspection requirements and a dedicated earliest-normal form for linear as well as uniform-copying transducers which can be constructed in polynomial time. As a consequence, equivalence of these transducers can be decided in polynomial time.
Applying these results to deterministic bottom-up transducers, we obtain that it is decidable whether or not their translations can be realized by deterministic uniform-copying top-down transducers without look-ahead (but with inspection) - or without both look-ahead and inspection. |
|Orateur||Helmut Seidl |
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