On Equality Up-to Constraints over Finite Trees, Context Unification, and One-Step Rewriting

On Equality Up-to Constraints over Finite Trees, Context Uni cation, and One-Step Rewriting

On rewrite constraints and context unification

We show that stratified context unification, which is one of the most expressive fragments of context unification known to be decidable, is equivalent to the satisfiability problem of slightly generalized rewriting constraints.

Rigid Tree Automata

We introduce the class of Rigid Tree Automata (RTA), an extension of standard bottom-up automata on ranked trees with distinguished states called rigid. Rigid states define a restriction on the computation of RTA on trees: two subtrees reaching the same rigid state in a run must be equal. RTA are able to perform local and global tests of equality between subtrees, non-linear tree pattern matchi...

Finite automata on unranked trees: extensions by arithmetical and equality constraints

The notion of unranked trees has attracted much interest in current research, especially due to their application as formal models of XML documents. In particular, several automata and logic formalisms on unranked trees have been considered (again) in the literature, and many results that had previously been shown for the ranked-tree setting have turned out to hold for the unranked-tree setting...

Solving Mixed Quantified Constraints over a Domain Based on Real Numbers and Herbrand Terms

Combining the logic of hereditary Harrop formulas HH with a constraint system, a logic programming language is obtained that extends Horn clauses in two different directions, thus enhancing substantially the expressivity of Prolog. The implementation of this new language requires the ability to test the satisfiability of constraints built up by means of terms and predicates belonging to the dom...