Tumbler (Project Xanadu)

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. 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/Bytes2. Links3. Bitmaps4. 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".

ee also

* Purple Numbers, a proposal to address paragraphs in Web pages.
* Cross-reference

External links

* cite web
url = http://www.udanax.com/green/febe/tumblers.html
title = Tumbler Arithmetic
work = Udanax.com™
accessmonthday = May 22 | accessyear = 2004
* cite web
title = The Xanadu model
url = http://xanadu.com/zigzag/fw99/XUmodel.html
accessmonthday = January 13 | accessyear = 2004
* cite web
title = Definitions
url = http://www.sunless-sea.net/wiki/Definitions
work = Sunless Sea
accessmonthday = January 30 | accessyear = 2006 "(Xanadu project wiki, restructured in August 2005)"
* cite journal
author = Theodor Holm Nelson
title = Xanalogical Structure. Needed Now More than Ever: Parallel Documents, Deep Links to Content, Deep Versioning, and Deep Re-Use
url = http://www.cs.brown.edu/memex/ACM_HypertextTestbed/papers/60.html
journal = ACM Computing Surveys
volume = 31 | issue = 4
date=December 1999
* cite web
title = Theodor Holm Nelson's Homepage
url = http://ted.hyperland.com/
accessmonthday = January 13 | accessyear = 2004