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キーワード:
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要旨:
We introduce a new class of finite automata. They are usual
bottom-up tree automata that run on DAG representations of finite
trees. We prove that the emptiness problem for this class of
automata is NP-complete. Using these automata we prove the
decidability of directional type checking for logic programs, and
thus we improve earlier results by Aiken and Lakshman. We also show an
application of these automata in solving systems of set constraints,
which gives a new view on the satisfiability problem for set
constraints with negative constraints.
