The solution of two star height problems for regular trees
نویسندگان
چکیده
Regular trees can he detined by two types of rational exprwions. For these two types w;isolve the star-height problem, i.e., we show how to construct a rational expression of minimal star-height from the minimal graph of the given tree (i.e., the analogue of the minimal deterministic automaton for regular languages). In one case, the minimal starheight is the rank (in the Sense of Eggan) of the minimal graph. There corresponds a characterization of the star-height of a preti---free regular language w.r.t. rational expressions of a special kind (called deterministic) as ,il~ r:::;L of its minimal deterministic automaton considered as a graph.
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