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A new kind of an acyclic pushdown automaton for an ordered tree is presented. The nonlinear tree pattern pushdown automaton represents a complete index of the tree for nonlinear tree patterns and accepts all nonlinear tree patterns which match the tree. Given a tree with n nodes, the number of such nonlinear tree patterns is O((2+v)n), where v is the number of variables in the patterns. We discuss time and space complexities of the nondeterministic nonlinear tree pattern pushdown automaton and a way of its implementation. The presented pushdown automaton is input-driven and therefore can be determinised.
Date of Conference: 18-21 Sept. 2011