Querying Unranked Trees with Stepwise Tree Automata

The problem of selecting nodes in unranked trees is the most basic querying problem for XML. We propose stepwise tree automata for querying unranked trees. Stepwise tree automata can express the same monadic queries as monadic Datalog and monadic second-order logic. We prove this result by reduction to the ranked case, via a new systematic correspondence that relates unranked and ranked queries.

• Type: Conference
• Year: 2004
• Where: RTA
• Authors: Julien Carme, Joachim Niehren, Marc Tommasi
• Keywords: Basic Querying Problem, RTA 2004, Stepwise Tree Automata, Theoretical Computer Science, Unranked Trees