The Boolean Closure of DR-Recognizable Tree Languages

  E. Jurvanen

Abstract:

  The family

 DRec of tree languages recognized by deterministic root-to-frontier (top-down) tree automata is not closed under unions or complements. Hence, it is not a variety of tree languages in the sense of Steinby. However, we show that the Boolean closure of DRec is a variety which is properly included in the variety Rec of all recognizable tree languages. This Boolean closure is also compared with some other tree language varieties.

 Gyenizse Pal 1996. Szeptember 4. Szerda 13:50:42 MET DST