Xanadu
*Ted Nelson's hypertext project.
1 Attempts at implementation
Interesting thread from John Ohno on attempts at implement Xanadu concepts - https://threadreaderapp.com/thread/1232381856294875137.html
Roam and wikis get namechecked as examples of regularly occurring attempts to rebuild Xanadu concepts, badly.. I suppose you could argue, at least they actually exist :)