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Enfilade (Xanadu)
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An Enfilade is a type of address used in Project Xanadu, as the rough equivalent of a Universal Resource IdentifierURI.
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An Enfilade is constructed as a series of tumblers. Each tumbler is a series of positive decimal integers, separated by periods. The tumblers themselves are separated by empty tumblers, or tumblers of length one whose value is zero. These are used only as separators.[1]
Tumblers contain an arbitrary number of integers, and Enfilades contain an arbitrary number of tumblers. In the xu88 system (now called Udanax Green[2]), tumblers could hold a maximum of 11 integers, though it is noted in the FeBe manual (the documentation for the system[2]) that this limitation was deprecated.[3]
The term Enfilade is not used explicitly in the FeBe document, but is instead noted indirectly in Xanalogical Structure and several other documents. In the aforementioned document, it is noted that xu88 was based on "General Enfilade Theory".
In 1972, xu72 introduced the concept of the Enfilade. This was called the "Model T Enfilade", and was used in a word-processing type interface. In 1976, xu76 implemented the "tightly coupled enfilade". 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. In 1992, xu92 implemented the modern concept of the ent. [4]