Pre-teen me was utterly fascinated with Xanadu, but that was before I learned about the computational and storage costs of data structures, and how large-scale human interaction with systems evolves. Now, I can't wrap my head around what Nelson promotes and what I extrapolate to a scaled-up global system. I'd really like to know from those more deeply immersed in the implementation of his vision how the following pieces are addressed, because I can't quite reconcile between the dribs and drabs I've pieced together of the internals and what I know of large-scale systems.

1. As near as I can tell, the ZigZag data structure at its core is a type of directed graph. Fast path traversal has always been a challenge for me with these at scale. When I want to pull a list of all referring/predecessor links, I'm either walking the graph, or maintaining a continuously-updated cross-reference lookup. I must be overlooking how he's solved this problem, because the kind of micro-payment environment he envisions seems to me to require knowing this information (is this what he calls a "cell"?) to compute the presented price of a piece of information derived from a foundation of other pieces of information.

2. How does transclusion work for non-text data like audio, video, rich media, chats, or in a generalized way, arbitrary data sets?

3. Was there ever a notion of transclusion quality or security? I don't see any acknowledgement in Nelson's design of the need to address bad actors abusing transclusion, giving rise to equivalents to spammers, trolls, phishers, etc. within the xanadocs environment.

4. What determines a cell? As near as I can tell (and my understanding is admittedly flawed), cells are decided by the author, but I must be wrong here. That seems a high cognitive load to make those decisions, and I don't see any support for crowd-defined cells, nor an API that would facilitate building such an interaction.

BTW, for those who lament the quiescence of the Gzz [1] project due to patent protection, it can pick up again now that the patent expired [2]. Whoever picks it up likely should read about the experiences of one of the original Gzz authors [3]. The most programmer-oriented write up of the data structure I could find [4] didn't erase my impression that Nelson's vision was fine for a small group, but doesn't address scaling up to the challenges we see on a global level.

It's still fascinating to think about, and I see value within a corporate environment, but I struggle seeing it staying useful in the public realm due to the this-is-why-we-can't-have-nice-things principle.

[1] http://www.nongnu.org/gzz/

[2] https://en.wikipedia.org/wiki/ZigZag_(software)#History

[3] http://lambda-the-ultimate.org/node/233#comment-1715

[4] https://hackernoon.com/an-engineers-guide-to-the-docuverse-d...