The memex (a portmanteau of "memory extender") is the name given by Vannevar Bush to the theoretical proto-hypertext computer system he proposed in his 1945 The Atlantic Monthly article As We May Think. The memex has influenced the development of subsequential hypertext and intellect augmenting computer systems.
A proto-hypertext system
Bush described the device as electronically linked to a library and able to display books and films from the library and automatically follow cross-references from one work to another.
The memex not only offered linked information to a user, but was also a tool for establishing the links. The technology used would have been a combination of electromechanical controls and microfilm cameras and readers, all integrated into a large desk. Most of the microfilm library would have been contained within the desk, but the user could add or remove microfilm reels at will.
The technology of the memex is often confused with that of hypertext. Although Bush's idea inspired the creation of hypertext, it is not considered to be hypertext. Indeed, Bush describes the memex and other visions of As We May Think as projections of current capabilities - in the spirit of Jules Verne or Arthur C. Clark's 1945 proposal to orbit geosynchronous satellites for global telecommunication. The memex proposed by Bush would create trails of links connecting sequences of microfilm frames, rather than links in the modern sense where a hyperlink connects a single word, phrase or picture within a document and a local or remote destination.
An associative trail as conceived by Bush would be a way to create a new linear sequence of microfilm frames across any arbitrary sequence of microfilm frames by creating a chained sequence of links in the way just described, along with personal comments and side trails. The closest analogy with the modern Web browser would be to create a list of bookmarks pointing to articles relevant to a topic, and then to have some mechanism for automatically scrolling through the articles (for example, use Google to search for a keyword, obtain a list of matches, and then use "open in new tab" in your browser and visit each tab sequentially). Modern hypertext systems with word and phrase-level linking offer more sophistication in connecting relevant information, but until the rise of wiki and other social software models, modern hypertext systems have rarely followed Bush in providing individuals with the ability to create personal trails and share them with colleagues - or publish them widely.
The memex would have features other than linking. The user could record new information on microfilm, by taking photos from paper or from a touch-sensitive translucent screen. A user could "... insert a comment of his own, either linking it into the main trail or joining it by a side trail to a particular item. ... Thus he builds a trail of his interest through the maze of materials available to him." A user could also create a copy of an interesting trail (containing references and personal annotations) and "... pass it to his friend for insertion in his own memex, there to be linked into the more general trail." As observers like Tim Oren have pointed out, the memex could be considered to be a microfilm-based precursor to the personal computer. The September 10, 1945 Life magazine article showed the first illustrations of what the memex desk could look like, as well as illustrations of a head-mounted camera, which a scientist could wear while doing experiments, and a typewriter capable of voice recognition and of reading text by speech synthesis. Taken together, these memex machines were probably the earliest practical description of what we would call today the "Office of the future".
Extending, storing and consulting the record of the species
Bush's vision for the memex extended far beyond a mechanism which might augment the research of one individual working in isolation. In Bush's vision the ability to connect, annotate and share both published works and personal trails would profoundly change the process by which the "world's record" is created and used:
Wholly new forms of encyclopedias will appear, ready made with a mesh of associative trails running through them, ready to be dropped into the memex and there amplified. The lawyer has at his touch the associated opinions and decisions of his whole experience, and of the experience of friends and authorities. The patent attorney has on call the millions of issued patents, with familiar trails to every point of his client's interest. The physician, puzzled by a patient's reactions, strikes the trail established in studying an earlier similar case, and runs rapidly through analogous case histories, with side references to the classics for the pertinent anatomy and histology. ... The historian, with a vast chronological account of a people, parallels it with a skip trail which stops only on the salient items, and can follow at any time contemporary trails which lead him all over civilization at a particular epoch. There is a new profession of trail blazers, those who find delight in the task of establishing useful trails through the enormous mass of the common record. The inheritance from the master becomes, not only his additions to the world's record, but for his disciples the entire scaffolding by which they were erected. -- As We May Think
Bush states that "technical difficulties of all sorts have been ignored," but that, "also ignored are means as yet unknown which may come any day to accelerate technical progress as violently as did the advent of the thermionic tube." Indeed, anyone who stops to consider the performance consequences of trail following - let along link directed pointer chasing - over a microfilm library of near universal scope should quickly come to the conclusion that microfilm is no more appropriate a technology for implementing AWMT's vision than Jules Verne's cannon is an appropriate technology for sending astronauts to the Moon. In both cases the vision may be more significant than the specific technology used to describe it. See Michael Buckland's conclusion: "Bush's contributions in this area were twofold: (i) A significant engineering achievement by the team under his leadership in building a truly rapid prototype microfilm selector, and (ii) a speculative article, 'As We May Think,' which, through its skillful writing and the social prestige of its author, has had an immediate and lasting effect in stimulating others." 
In "Memex: Getting Back on the Trail", Tim Oren argues that Bush's original vision expressed in AWMT describes a "... private device into which public encyclopedia's and colleague's trails might be inserted to be joined with the owner's own work."
However, in Bush's manuscript draft of "Memex II" of 1959 (also published in ), Bush says, "Professional societies will no longer print papers..." and states that individuals will either order sets of papers to come on tape - complete with photographs and diagrams - or download 'facsimiles' by telephone. Each society would maintain a 'master memex' containing all papers, references, tables "intimately interconnected by trails, so that one may follow a detailed matter from paper to paper, going back through the classics, recording criticism in the margins."
Missing features: search and metadata
The AWMT paper did not describe any automatic search, nor any universal metadata scheme such as a standard library classification or a hypertext element set like the Dublin core. Instead, when the user made an entry, such as a new or annotated manuscript, typescript or image, he was expected to index and describe it in his personal code book. By consulting his code book, the user could retrace annotated and generated entries.
Michael Buckland, in an article published in 1992, suggested that the memex was severely flawed because Bush did not thoroughly understand information science and had a low opinion of indices and classification schemes: "Bush thought that the creation of arbitrary associations between individual records was the basis of memory, so he wanted 'memo(ory-)ex', or 'Memex instead of index'. The result was a personalized, but superficial and inherently self-defeating design."
One must note that Buckland was writing at the very infancy of the world wide web which was first introduced in 1991 and not widely experienced until 1993. At introduction, the web was predominantly link based (associational). Classification and indexing efforts followed, with automatic indexing in the form of search engines quickly gaining prominence over classification efforts, while both remained complementary to links. Whether Buckland would not have applied this same denigration of Memex equally to the world wide web as it flourished in its early years is unclear. While it has since become clear that an index (search engine) is the most expedient entre into unfamiliar subject matter, associational links have remained an effective navigational method for obtaining broad or deep coverage of a subject area under study. In the Internet era, links are typically incorporated during authorship, while indices are almost always mechanical. Bush's unwillingness to place greater prominence on indices might have stemmed from his inability to visualize a near-term mechanical process for their creation, rather than a failure to recognize their utility once obtained.
Buckland also states that Bush's vision should be viewed from the historical perspective of microfilm technology developed prior to 1945 rather than based on the power and versatility of digital computer technology developed after 1945. Buckland summarizes the very advanced pre-World War II development of microfilm based rapid retrieval devices, specifically the microfilm based workstation proposed by Leonard Townsend in 1938 and the microfilm and photoelectronic based selector, patented by Emmanuel Goldberg in 1931. Buckland states: "The literature on documentation in the 1930s was as preoccupied with microfilm technology as it is now with computer technology and for the same reason, each being the most promising information retrieval technology of the time." Buckland notes that Bush directed creation of a photoelectronic microfilm 'rapid selector' at MIT in 1938-1940 using stroboscope technology pioneered by his colleague Harold Edgerton. Buckland suggests that Bush and his team may not have been aware of Goldberg's earlier work when they built their 1938-1940 prototype, but that IBM researchers and Bush's Eastman Kodak Research Laboratory sponsor certainly were. Buckland concludes: "We speculate that Bush did not independently originate the notion of an electronic microfilm selector, although that was possible. It is not surprising that the same invention sometimes occurs independently and more or less simultaneously when a need is present and the technology becomes ripe."
This idea directly influenced computer pioneers J.C.R. Licklider (see his 1960 paper Man-Computer Symbiosis), Douglas Engelbart (see his 1962 report Augmenting Human Intellect), and also led to Ted Nelson's groundbreaking work in concepts of hypermedia and hypertext.
As We May Think also predicted many kinds of technology invented after its publication in addition to hypertext such as personal computers, the Internet, the World Wide Web, speech recognition, and online encyclopedias such as Wikipedia: "Wholly new forms of encyclopedias will appear, ready-made with a mesh of associative trails running through them, ready to be dropped into the memex and there amplified."
Bush's influence is still evident in research laboratories of today in both Gordon Bell's project, MyLifeBits (from Microsoft Research) as well as Richard Furuta and Frank Shipman's Walden's Paths project (from Texas A&M University). Both projects have implemented path-based systems reminiscent of the Memex.
- As We May Think
- Vannevar Bush
- Douglas Engelbart
Reactive Engine, NLS and Sketchpad
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- "As We May Think" - The original article from the Atlantic Monthly archives
- "As We May Think" - The original article from the Atlantic Monthly archives
- Michael K. Buckland "Emanuel Goldberg, Electronic Document Retrieval, And Vannevar Bush's Memex". Journal of the American Society for Information Science 43, no. 4 (May 1992): 284–294
- Nyce, James M.; Kahn, Paul (eds.) "From Memex to Hypertext: Vannevar Bush and the Mind's Machine". San Diego, London (...) 1991. [A reprint of all of Bush's texts regarding Memex accompanied by related Sources and Studies]
- Engines of Creation (1986) by K. Eric Drexler.