An enfilade is a basic structure used in Project Xanadu to represent documents as a tree structure. They were invented in 1970 and revised several times since. Until 1999, the details of enfilades were a trade secret, with only cryptic mentions in published literature. A newer development of enfilades called the ent is now being used in Xanadu development.
The key concepts are dsps and wids, where dsps are displacements or offsets (giving the relative location of something in the tree from some other place), while wids are ranges of the tree which can be treated as objects.
Editing is done by splitting trees into subtrees which can be rearranged. A subtree can be multiply linked from different places, allowing a set of data to be used more than once, inheriting all its properties.
The versions of enfilades that have been used are:
- Model-T Enfilade