Publication details

Saarland University Computer Science

Parallelism and Tree Regular Constraints

Joachim Niehren, Mateu Villaret

International Conference on Logic for Programming, Artificial Intelligence and Reasoning, Vol. 2514 of LNAI, pp. 311--326, springer, October 2002

Parallelism constraints are logical descriptions of trees. Parallelism constraints subsume dominance constraints and are equal in expressive power to context unification. Parallelism constraints belong to the constraint language for lambda structures (CLLS) which serves for modeling natural language semantics. In this paper, we investigate the extension of parallelism constraints by tree regular constraints. This canonical extension is subsumed by the monadic second-order logic over parallelism constraints. We analyze the precise expressiveness of this extension on basis of a new relationship between tree automata and logic. Our result is relevant for classifying different extensions of parallelism constraints, as in CLLS. Finally, we prove that parallelism constraints and context unification remain equivalent when extended with tree regular constraints.

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