Vannevar Bush, in 1945, provided the initial vision [1]:
It affords an immediate step, however, to associative indexing, the basic idea of which is a provision whereby any item may be caused at will to select immediately and automatically another. This is the essential feature of the memex. The process of tying two items together is the important thing. ... It is exactly as though the physical items had been gathered together from widely separated sources and bound together to form a new book. It is more than this, for any item can be joined into numerous trails.
His concepts were picked up by Englebart, who read Bush's article, and thought about it in the context of his WWII radar technician work [2]:
When I first heard about computers, I understood from my radar experience during the war that if these machines show you information on printouts, they could show that information on a screen. When I saw the connection between a television-like screen, an information processor, and a medium for representing symbols to a person it all tumbled together in about half an hour. I went home and sketched a system in which computers would draw symbols on the screen and I could steer through different information spaces with knobs and levers and look at words and data and graphics ...
By 1968, Engelbart had built a hypertext system that was more advanced than many today - supporting multiple simultaneous users updating and viewing a shared information space - with a mouse, multiple windows on a screen, electronic mail, computer conferencing, annotations, etc.
Ted Nelson, still today the visionary showman, was also influenced by Bush, and worked in the 1960s with the group at Brown (whose work later led to Intermedia). He coined the terms hypertext (referring to nonlinear writing) and hypermedia [4]:
`Hyper' to most scientists and mathematicians means extended and generalized, as in hyperspace, hyperdimensional, hypercube, and even hyperchess ... . Thus hypertext would clearly be the extended, generalized form of writing.
His Xanadu system was in some senses a forerunner of efforts to build a worldwide digital library. Nelson has been especially interested in issues of intellectual property, pluralism and egalitariansism, so that all can write and annotate, and all can receive just recompense. He hoped hypertext would help unify and organize, leading to a docuverse instead of individual islands of information. Nelson is the originator of many of the ideas found in today's hypertext systems, and made usable suggestions for future implementations, covering structure, interfaces, shared use, etc.
Other important visionary statements include Alan Kay's Dynabook and ideas relating to his Vivarium Project. John Sculley's Knowledge Navigator extends us further into what Vinton Cerf and Robert Kahn have called Knowbots, and may lead to various intelligent agents and personal assistants being developed by Apple and other companies.
Several important early hypertext systems arose in the 1970s and early 1980s. Zog, later KMS, pushed the idea of ``frames'' which are often screen sized chunks. NoteCards, from Xerox PARC, used the model of smaller chunks, much like 3x5 cards used by information analysts, which later led to Apple's HyperCard (in 1987) and its many clones. In addition to this ``cardshark'' movement, there was also the ``Holy Scroller'' group, developing systems like OWL's Guide. These use scrolling windows for sequential components, and pop-up windows for annotations, glossary references, etc. Thus, a document might first appear in outline form, but when a section is selected with a mouse, the scrolling window contents are increased to have the section contents instead of the section title.
With the emergence of HyperCard, and the Hypertext '87 conference, a visible hypertext community arose, both on the commercial and the research side. Hypertext capabilities have been added even to page-oriented systems like Adobe Acrobat. With the development of the World-Wide Web and tools like Mosaic, people first connected hypertext technology into the Internet is a fashion that began to give expression to the global vision of Bush and Nelson.