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+## Obsolete
+
+The structures described by the page were removed around June 2007, replaced by the simpler [DirectoryNode](DirectoryNode) approach. However, the concepts this page describes are still applicable, and some of this approach may yet live again.
+
 ## Subtrees
 
 In Tahoe, a virtual drive is made up of a collection of "subtrees". Each subtree has zero or more levels of internal directory nodes. Each directory node is a mapping from child name to either another directory node or to a "child specification string" that references another subtree or an actual file.