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arXiv 1302.6960cs.LOcs.FL
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混合局部和全局约束的树自动机的可判定类--模平坦理论

Decidable Classes of Tree Automata Mixing Local and Global Constraints Modulo Flat Theories

Luis Barguñó, Carles Creus, Guillem Godoy, Florent Jacquemard, Camille Vacher

摘要:

我们定义了一类排序树自动机TABG,它推广了Bogaert和Tison(1992)兄弟之间的局部测试树自动机和Filiot等人(2007)的全局等式和不等式约束(TAGED)。TABG可以测试兄弟子项之间以及位置由计算期间达到的状态定义的子项之间的给定平坦方程理论的相等性和不等性。特别地,TABG可以检查到达给定状态的所有子项是否不同。此约束与XML文档的一元键约束有关,这意味着给定类型的每两个不同位置具有不同的值。我们证明了TABG的空性问题的可判定性。这特别解决了TAGED的空性的可判定性的公开问题。我们进一步扩展我们的结果,允许全局算术约束计数的出现次数的一些状态或不同的等价类的子项(模一个给定的平面方程理论)达到一些状态在计算过程中的数量。我们还调整模型,以无序有序的条款。作为我们的结果TABG的后果,我们证明了一元二阶逻辑的一个片段的可判定性扩展与谓词之间的平等和不平等的子树,和基数的树。

英文摘要:

We define a class of ranked tree automata TABG generalizing both the tree automata with local tests between brothers of Bogaert and Tison (1992) and with global equality and disequality constraints (TAGED) of Filiot et al. (2007). TABG can test for equality and disequality modulo a given flat equational theory between brother subterms and between subterms whose positions are defined by the states reached during a computation. In particular, TABG can check that all the subterms reaching a given state are distinct. This constraint is related to monadic key constraints for XML documents, meaning that every two distinct positions of a given type have different values. We prove decidability of the emptiness problem for TABG. This solves, in particular, the open question of the decidability of emptiness for TAGED. We further extend our result by allowing global arithmetic constraints for counting the number of occurrences of some state or the number of different equivalence classes of subterms (modulo a given flat equational theory) reaching some state during a computation. We also adapt the model to unranked ordered terms. As a consequence of our results for TABG, we prove the decidability of a fragment of the monadic second order logic on trees extended with predicates for equality and disequality between subtrees, and cardinality.

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