Tumblers

Tumblers were proposed by Ted Nelson in "Literary Machines" as a means to address all contents and links (as well as ranges and sets of contents and links) within the Xanadu system. more...

Tumblers were used in the Xanadu FEBE (Front End - Back End) protocol in a manner similar to the use of URIs between web browsers and servers.

A tumbler is a unique numerical address of an interesting artifact. The address resembles an IP address, but is much larger and has much more detailed structure. The structure looks like this.

1. < node >.0. < user >.0. < document >.0. < element >

The "1." is used in order to mark the start of a new address. The individual fields of the address are divided with ".0." so that they can be arbitratily long. Each < element > has the format "n. n. ... . n", a hierarchy of subaddresses.

The last element denotes the special kind of element, for example:

1. Text/Bytes 2. Links 3. Bitmaps 4. etc.

The 9287th byte of this version of the document would be 1.2368.792.6.0.6974.383.1988.352.0.75.2.0.1.9287 and the 356th link would be 0.2.356 on the end instead.

Tumblers are only issued once and never changed again. The structure can grow at will, the address space is practically infinite.

Nelson also introduces the concept of "spans", and the idea of direction. One can speak of "2 chapters back" or "300 bytes forward".

Read more at Wikipedia.org