On Regular Tree Languages and Deterministic Pushdown Automata. 
Abstract: 
The theory of formal string languages and of formal tree languages are both 
important parts of the theory of formal languages. Regular tree languages are 
recognized by finite tree automata. Trees in their postfix notation can be seen 
as strings. This paper presents a simple transformation from any given 
(bottom-up) finite tree automaton recognizing a regular tree language to a 
deterministic pushdown automaton accepting the same tree language in postfix 
notation. The resulting deterministic pushdown automaton can be implemented 
easily by an existing parser generator because it is constructed for an LR(0) 
grammar, and its size directly corresponds to the size of the deterministic 
finite tree automaton. The class of regular tree languages in postfix notation 
is a proper subclass of deterministic context-free string languages. Moreover, 
the class of tree languages which are in their postfix notation deterministic 
context-free string languages is a proper superclass of the class of regular 
tree languages.