March 9, 2019

A Lost Treasure of Xanadu

Some years ago I found the cover sheet to a lost Xanadu architecture document, which I turned into this blog post for your amusement. Several people commented to me at the time that they wished they could see the whole document it was attached to. Alas, it appeared to have vanished forever.

Last weekend I found it! I turned up a copy of the complete document while sorting through old crap in preparation for having to move in the next few months. Now that I’ve found it I’m putting it online so it can get hoovered up by the internet hive mind. This is the paradox of the internet — nothing is permanent and nothing ever goes away.

It is here.

This is a document I wrote in early 1984 at the behest of the System Development Foundation as part of Xanadu’s quest for funding. It is a detailed explanation of the Xanadu architecture, its core data structures, and the theory that underlies those data structures, along with a (really quite laughable) project plan for completing the system.

At the time, we regarded all the internal details of how Xanadu worked as deep and dark trade secrets, mostly because in that pre- open source era we were stupid about intellectual property. As a consequence of this foolish secretive stance, it was never widely circulated and subsequently disappeared into the archives, apparently lost for all time. Until today!

What I found was a bound printout, which I’ve scanned and OCR’d. The quality of the OCR is not 100% wonderful, but as far as I know no vestige of the original electronic form remains, so this is what we’ve got. I’ve applied minimal editing, aside from removing a section containing personal information about several of the people in the project, in the interest of those folks’ privacy.

Anyone so inclined is quite welcome, indeed encouraged, to attempt a better conversion to a more suitable format. I’d do that myself but I really don’t have the time at the moment.

This should be of interest to anyone who is curious about the history of Project Xanadu or its technical particulars. I’m not sure where the data structures rank given the subsequent 35 or so years of advance in computer science, but I think it’s still possible there’s some genuinely groundbreaking stuff in there.


Thank you for posting this.

How much further in the listed plan did you get before it got shut down?

Quite a long way, actually, though not necessarily according to the development plan per se that’s described in this document. The funding from System Development Foundation was used up around the time this was written (writing this document was part of the effort to get additional funding beyond that). However, Autodesk picked it up in 1988 and funded quite a robust development team until 1992 sometime. See for more, including the code from the two generations of implementation, which have now been open sourced.

Hey ~ interesting site! Haven’t heard from Ted Nelson for awhile, know what’s he up to these days?

He’s interviewed in this documentary:

Werner Herzog says Ted is one of the sanest persons he’s ever met.

Anyone so inclined is quite welcome, indeed encouraged, to attempt a better conversion to a more suitable format.

I’m interested in doing a new edition of this text, keeping the wording intact but using variable-width fonts, vector diagrams instead of ASCII like the one in page 5, etc.

For that I would need a clear license, ideally the Creative Commons Attribution-ShareAlike:

If you get me that, I’ll start immediately.

That would be truly awesome. All the Xanadu materials, including this, are released under the MIT license. The terms of the MIT license are sufficiently loose that you would be free to put a derivative work un Creative Commons if you so wish.

I’m almost at the 50% mark and have a couple of questions:

On page 9, what do you mean by “Reps’ subtree sharing”?

On page 31, in the last paragraph there is some mangled text in the original:

“writings — documents — in the form of papers, articles, book, tcialrrt, esonde

explicit and implicit connections — links — such as citations, references,“

Can you figure out what you intended to write?

Alas, I wrote this document 35 years ago. The first thing seems to be an internal editorial comment about something that should be expanded on, but I really have no idea what. The second thing is some kind of mangling that must have happened when the document was sent to the printer; this was originally printed on a daisy wheel printer attached via a serial interface, and so you’d sometimes get noise on the wire that would cause thing kind of thing. Unfortunately, I have no clue what the original text might have been.

All right, then I’ll fill it in with frog DNA plausible words, and a note describing the changes.

The note says:

In the original, a couple of words got mangled and it read “articles, book, tcialrrt, esonde explicit and implicit connections”. I have replaced “tcialrrt” with “journals” which has the same number of letters and fits the “scientific literature” example subject, and “esonde” with “and” which fits the expected line length and works grammatically.

That sounds like a good way to handle it. It would be cool to use frog DNA though.

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