I don't think many people would argue that Nelson isn't a visionary, but when push comes to shove, there is an uncomfortable amount of truth in Steve Jobs's oft-cited quip, "Real artists ship." After 50 years, Project Xanadu not only isn't in a production-ready state, the "best demo" available is described on the xanadu.com web site as "beyond fixing." The sample EDL documents on the site do a good job of demonstrating what Nelson had in mind with "transclusion" and two-way links, but it is
much harder to tell at a glance what the relationship of the source is to the output than it is with HTML, and at least as implemented, EDLs look awfully brittle.
Maybe Xanadu as envisioned would have been better than the web we have now, but what we have as ostensible working proof of that isn't incredibly convincing. Okay, I could link to any text on another web page, not just text with "anchor" links, and the text I linked to would be highlighted. That's nice, but is it essential? And I can transclude text from any other page, which is coo, but man, Nelson seems to stubbornly ignore the ramifications -- or perhaps think commerce and law will rearrange itself suitably to accommodate his vision. "Publishers of original content are free to require payment, or not"; what's the mechanism? What if I just don't want you to transclude text from my document, or only want to allow transcluding certain parts? How are EDLs updated when transcluded documents change? How come, after fifty years, these fundamental questions are still answered with lines like "[Page and document logic] is defined by the data structure, which we will publish when ready"? Has anyone associated with Xanadu considered even basic HTML 2.0-level presentation aspects like tables, images and fonts?
I can't help but think Ted Nelson is the archetypal poster child for "the perfect is the enemy of the good." He's not the Jef Raskin of Apple because, at the end of the day, Raskin was willing to work with other people and make compromises to get some of his vision out the door. Xanadu's failure -- and by all practical measures, it is indeed a failure -- isn't due to the MIT Media Lab, or Tim Berners-Lee, or Apple, or Microsoft, or its variously brilliant-slash-flaky development teams. It's because they never. Ever. Shipped.