From time to time developers of (database) applications will encounter, explicitly or implicitly, structures such as trees, graphs, and networks. Such applications can, for instance, relate to bills of material, organization charts, networks of (rail)roads, networks of conduit pipes (e.g., plumbing, electricity), telecom networks, and data dictionaries. Algorithms on such data structures often require recursion or iteration where the number of repetitions is unknown a priori. Such algorithms are usually implemented in a third generation language (3GL) and, therefore, are typically “record-at-a-time”. A vast amount of theoretical work on recursive queries in logical languages (and related problems in research prototypes) is available, but these “extensions” typically are not available in commercial database management systems. Hence, they do not directly help the database developer “in the field” who has available only “ordinary” SQL with a few enhancements.