Edward L. Robertson Lawrence V. Saxton Dirk Van Gucht Stijn Vansummeren Structural Recursion on Ordered Trees and List-Based Complex Objects. 344-358 2007 conf/icdt/2007 ICDT http://dx.doi.org/10.1007/11965893_24 db/conf/icdt/icdt2007.html#RobertsonSGV07