sentences:  In 1980, the xu80 system introduced the "ent", described as a versioning enfilade.In 1988, the xu88 system utilized the concept of "General Enfilade Theory" of Mark S. Miller, Stuart Greene and Roger Gregory, described as "generating data management trees with an upwardly propagating search property and simultaneously a downwardly imposable structural property".The xu88 also extended the concept of the Enfilade over a distributed network, introduced two-dimensional Enfilades, and implemented an algorithm for searching the entire docuverse for overlapping Enfilade spans.