It was a vision in a dream. A computer filing system which would store and deliver the great body of human literature, in all its historical versions and with all its messy interconnections, acknowledging authorship, ownership, quotation and linkage. Like the web, but much better: no links would ever be broken, no documents would ever be lost, copyright and ownership would be scrupulously preserved. This vision is actually older than the web, and aspects of it are older than personal computing: it belongs to hypertext pioneer Theodore Holm Nelson, who dubbed the project Xanadu in 1967.