Transition Graphs of Rewriting Systems over Unranked Trees

We investigate algorithmic properties of infinite transition graphs that are generated by rewriting systems over unranked trees. Two kinds of such rewriting systems are studied. For the first, we construct a reduction to ranked (binary) trees via an encoding and to standard ground tree rewriting, thus showing that the generated classes of transition graphs coincide. In the second rewriting formalism, we use subtree rewriting combined with a new operation called flat prefix rewriting and show that strictly more transition graphs are obtained while the reachability problem remains decidable.

• Type: Conference
• Year: 2007
• Where: MFCS
• Authors: Christof Löding, Alex Spelten
• Keywords: Infinite Transition Graphs, MFCS 2007, Rewriting Formalism, Transition Graphs