Forgotten Forefather: Paul Otlet

Written by: Alex Wright

One rainy afternoon in 1968, a young Australian graduate student named Boyd Rayward stepped into an abandoned office in the Parc Leopold in Brussels, Belgium. Inside, he discovered “a cluttered, musty, cobwebbed office into which the rain leaked—and one day flooded—causing the attendant then on hand to have a kind of epileptic seizure.”1 Piled high to the ceiling were dusty stacks of books, files and manuscripts: the intellectual flotsam of a seemingly disorganized old scholar.

The previous occupant, Paul Otlet, had been dead for nearly twenty-five years. A bibliographer, pacifist and entrepreneur, Otlet had in his heyday been feted as a great man, enjoying the company of Nobel laureates and even playing a role in the formation of the League of Nations. But by the time of his death in 1944, he had lived long enough to see his reputation fade to near-obscurity, seen his greatest ambition fail, and suffered the final humiliation of watching the Nazis cart away and destroy much of his life’s work. When he finally died a few months before the end of the war, hardly anyone noticed.

Who was Paul Otlet? Meet the forgotten forefather of information architecture.

The web that wasn’t

In 1934, years before Vannevar Bush dreamed of the memex, decades before Ted Nelson coined the term “hypertext,” Paul Otlet envisioned a new kind of scholar’s workstation: a moving desk shaped like a wheel, powered by a network of hinged spokes beneath a series of moving surfaces. The machine would let users search, read and write their way through a vast mechanical database stored on millions of 3×5 index cards.2

This new research environment would do more than just let users retrieve documents; it would also let them annotate the relationships between one another, “the connections each [document] has with all other [documents], forming from them what might be called the Universal Book.”3

Otlet imagined a day when users would access the database from great distances by means of an “electric telescope” connected through a telephone line, retrieving a facsimile image to be projected remotely on a flat screen.

In Otlet’s time, this notion of networked documents was still so novel that no one had a word to describe these relationships, until he invented one: “links.”

Otlet envisioned the whole endeavor as a great “réseau”—web—of human knowledge.

The Universal Decimal Classification

Although generations of philosophers had tried to solve the problem of classifying human knowledge—including Bacon, Wilkens, and Linnaeus—it was not until the middle of the 19th century that the problem came to a practical head. The industrialization of the printing business, coupled with the advent of cheap binding materials, spurred an explosion in publishing no less disruptive than the advent of Gutenberg’s press 400 years earlier.

Faced with an onslaught of new texts, nineteenth century scholars and bibliographers began to wrestle again with the problem of classification. Catalogers like Panizzi, Dewey and Ranganathan all devised elaborate subject schemes, laying the foundations of modern library and information science.

In 1895, Otlet and Henri La Fontaine established the Repertoire Bibliographique Universel (RBU), an ambitious attempt at developing a master bibliography of the world’s accumulated knowledge. Otlet recognized from the beginning that the success of the whole undertaking would depend largely on the usefulness of its conceptual software, the classification system.

After evaluating the classification systems then in use, such as Dewey Decimal and the British Museum system, Otlet concluded that they all shared a fatal flaw: they were designed to guide readers as far as the individual book—but no further. Ranganathan had voiced the ethos of modern cataloging when he said: “every reader his or her book, and every book its reader.” But once book and reader were matched, they were left pretty well to their own devices.

Otlet wanted to go a step further. He wanted to penetrate the boundaries of the books themselves, to unearth the “substance, sources and conclusions” inside.

Taking the Dewey Decimal system as his starting point, Otlet began developing what came to be known as the Universal Decimal Classification, now widely recognized as the first—and one of the only—full implementations of a faceted classification system.

While Ranganathan rightly receives credit as the philosophical forbear of facets, Otlet was the first to put them to practical use.

Facets of the Universal Decimal Classification

Facts: Empirical observations or assertions.
Interpretation: Analysis or conclusions, derived from “facts.”
Statistics: Measured, quantifiable data.
Sources: Citations or references.

Today, the UDC comprises over 62,000 individual classifications, translated into over 30 languages (one reason for its popularity outside the U.S.). The UDC’s current top-level classes include:

0 Generalities. Science, knowledge, organization, computer science
1 Philosophy. Psychology
2 Religion. Theology
3 Social sciences. Law
4 [Under development]
5 Mathematics and natural sciences
6 Applied sciences. Medicine. Technology
7 The arts. Recreation. Entertainment. Sport
8 Language. Linguistics. Literature
9 Geography. Biography. History

So, for example,

004 Computer science
004.8 Artificial intelligence
004.89 Artificial intelligence application systems
004.891 Expert systems
004.891.2 Consultation expert systems4

In addition to the so-called Main Tables of subject headings, UDC also supports a series of Auxiliary Tables allowing for the addition of facets. These tables provide notations for place, language, physical characteristics, and for marking relationships between topics using a set of “connector” signs such as “+,” “/” and “:”.

The UDC’s capacity for mapping relationships between ideas—for constructing the “social space” of a document—provides a dimension of use not supported in other purely topical classification schemes. As the Universal Decimal Classification Consortium puts it:

UDC’s most innovative and influential feature is its ability to express not just simple subjects but relations between subjects … In UDC, the universe of information (all recorded knowledge) is treated as a coherent system, built of related parts, in contrast to a specialised classification, in which related subjects are treated as subsidiary even though in their own right they may be of major importance.5

The Mundaneum

In 1910, in the wake of the Brussels world’s fair, Otlet and LaFontaine created an installation at the Palais du Cinquantenaire of the Palais Mondial.

Originally envisioned as the centerpiece of a new “city of the intellect,” the Mundaneum was to be the hub of a utopian city that housed a society of the world’s nations.

In 1919, shortly after the end of World War I, Otlet successfully lobbied King Albert and the Belgian government to furnish a new home for the Mundaneum, taking over 150 rooms in Brussels’ Cinquantenaire. At the time, not coincidentally, Belgium was lobbying to host the nascent League of Nations’s new headquarters. Hoping to help his country take center stage in wooing the new organization, Otlet pitched his project as the centerpiece of a new “world city.” Inside the new Mundaneum, he began to assemble his vast “documentary edifice,” eventually comprising over 12 million individual index cards and documents.

At the time, the 3×5 index card represented the latest advance in information storage technology: a standardized, easily manipulated vessel for housing individual nuggets of data. So, Otlet’s réseau began taking shape in the form of an enormous collection of index cards, filed away in a sprawling array of cabinets.

The effort met with early success, even attracting a healthy business in mail-order research services, in which users would submit search queries for a fee (27 francs per 1000 cards retrieved). The service attracted over 1500 requests a year on subjects from boomerangs to Bulgarian finance.6

But by 1924, the Belgian government had lost patience with the project, especially after the newly formed League of Nations chose Geneva over Brussels as its headquarters—and thus robbing the Mundaneum of one of its primary raisons d’etre. Otlet had to relinquish his original location, moving the Mundaneum to succession of smaller quarters, even landing briefly, ignominiously, in a parking garage. After a series of fiscal struggles and management missteps, Otlet finally faced the difficult but unavoidable choice of shutting down operations in 1934. A few years later, Nazi troops came and carted away the remnants—to make way for an exhibition of Third Reich art.

After Otlet’s death in 1944, what survived of the original Mundaneum was left to languish in an old anatomy building of the Free University in the Parc Leopold, all but forgotten. Over the ensuing half-century, more than 70 tons’ worth of its original contents were destroyed. Finally, in the mid-1990s, a group of volunteers began resurrecting Otlet’s original vision, hoping to preserve and refurbish the original Mundaneum.

In 1996, the new Mundaneum opened in Mons, Belgium, serving primarily as a museum to preserve Otlet’s legacy and his vision of the “Universal Book.” While today’s Mundaneum serves primarily as a museum and learning center, rather than as a working incarnation of Otlet’s original plan, the new institution does an admirable job of perpetuating his legacy, and reminding us of Otlet’s premonitory vision of a worldwide networked information environment.

The Traité

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In a bitter irony, the Mundaneum’s 1934 closure coincided almost exactly with the publication of Otlet’s masterwork, the Traité de documentation, a manifesto crystallizing 40 years’ worth of writing and research into the possibilities of networked information structures.

Otlet biographer Boyd Rayward describes the Traité as ”perhaps the first systematic, modern discussion of general problems of organising information.”7

With the faceted philosophy of the UDC as backdrop, the Traité posited a universal “law of organization” declaring that no document could be properly understood by itself, but that its meaning becomes clarified through its influence on other documents, and vice versa. “[A]ll bibliological creation,” he said, “no matter how original and how powerful, implies redistribution, combination and new amalgamations.”8

While that sentiment may sound postmodernist in spirit, Otlet was no semiotician; rather, he simply believed that documents could best be understood as three-dimensional,9 with the third dimension being their social context: their relationship to place, time, language, other readers, writers and topics. Otlet believed in the possibility of empirical truth, or what he called “facticity”—a property that emerged over time, through the ongoing collaboration between readers and writers. In Otlet’s world, each user would leave an imprint, a trail, which would then become part of the explicit history of each document.

Vannevar Bush and Ted Nelson would later voice strikingly similar ideas about the notion of associative “trails” between documents. Distinguishing Otlet’s vision from the Bush-Nelson (and Berners-Lee) model is the conviction—long since fallen out of favor—in the possibility of a universal subject classification working in concert with the mutable social forces of scholarship.

Otlet’s vision suggests an intellectual cosmos illuminated both by objective classification and by the direct influence of readers and writers: a system simultaneously ordered and self-organizing, and endlessly re-configurable by the individual reader or writer.

Does Otlet still matter?

Jorge Luis Borges’ fictional Library of Babel was a place containing “all the possible combinations of the twenty-odd orthographical symbols … the translation of every book in all languages, the interpolations of every book in all books.”10

For Borges, the universal library was a literary conceit, but for Otlet it was an achievable dream: an “edifice containing all the books and the information together with all the resources of space needed to record and manage them.”11

Otlet also recognized the practical importance of “search and retrieval performed by an appropriately qualified permanent staff.” Substitute the word “Google” for “permanent staff,” and Otlet’s vision starts sounding a lot like the World Wide Web.

While it would be an exaggeration to claim that Otlet exerted a direct influence on the later development of the Web, it would be no exaggeration to say that he anticipated many of the problems we find ourselves grappling with: the explosion of published information, the limitations of current delivery and storage mechanisms, the desperate need for a classificatory framework to help us store, manage and interpret humanity’s collective intellectual capital—and, perhaps, the limits of self-organizing systems.

In the Web’s current incarnation, individual “authors” (meaning both people and institutions) maintain fixed documents, over which they exert direct control. Each document is essentially a fait accompli, with its own self-determined set of relationships to other documents. It takes a meta-application like Google or Yahoo! to discover the broader relationships between documents (usually through some combination of syntax, semantics and reputation). But those relationships, however sophisticated the algorithm used to determine them, remain largely unexposed to the end user, never becoming an explicit part of the document’s history.

Would Otlet’s Web have turned out any differently? We may yet find out. With the advent of the Semantic Web and related technologies like RDF/RSS, FOAF, and ontologies, we are moving towards an environment where social context is becoming just as important as topical content. Otlet’s vision holds out a tantalizing possibility: marrying the determinism of facets with the relativism of social networks.

In Otlet’s last book, Monde, he articulated a final vision of the great “réseau” that might as well serve as his last word:

Everything in the universe, and everything of man, would be registered at a distance as it was produced. In this way a moving image of the world will be established, a true mirror of his memory. From a distance, everyone will be able to read text, enlarged and limited to the desired subject, projected on an individual screen. In this way, everyone from his armchair will be able to contemplate creation, as a whole or in certain of its parts.12


  1. Rayward, “The Case of Paul Otlet, Pioneer of Information Science, Internationalist, Visionary: Reflections on Biography,” Journal of Librarianship and Information Science 23 (September 1991):135-145
  2. Rayward, “Visions of Xanadu: Paul Otlet (1868-1944) and Hypertext,” JASIS 45 (1994):235-250
  3. Otlet 1934 quoted in Rayward 1994
  4. Universal Decimal Classification Consortium, UDC flyer
  5. Universal Decimal Classification Consortium, “About the UDC.”
  6. Rayward, “Visions of Xanadu”
  7. Otlet quoted in Day, “Paul Otlet’s Book and the Writing of Social Space “
  8. Buckland, “Information Retrieval of More than Text” JASIS 42, 586-588
  9. Rayward, “Anticipating the Digital World: Paul Otlet and his Paper Internet”
  10. Borges, “The Library of Babel” in Labyrinths, p. 54
  11. Otlet, Traité de Documentation
  12. Otlet, Monde, pp. 390-391


Borges, Jorge Luis. “The Library of Babel,” in Labyrinths. New Directions, 1962. pp. 51-58.

Buckland. Michael. Information retrieval of more than text. Journal of the American Society for Information Science 42 (1991): 586-588

Day, Ron. “Paul Otlet’s Book and the Writing of Social Space.“ Journal of the American Society for Information Science, April 1997.

Otlet, Paul. Traite de documentation. Brussels: Editiones Mundaneum, 1934.
Otlet, Paul. Monde: essai d’universalisme: connaissance du monde, sentiment du monde, action organisée et plan du monde. Brussels: Editiones Mundaneum, 1935.
Rayward, W. Boyd. “The Case of Paul Otlet, Pioneer of Information Science, Internationalist, Visionary: Reflections on Biography,” in Journal of Librarianship and Information Science 23 (September 1991):135-145.

Rayward, W. Boyd. “Anticipating the Digital World: Paul Otlet and his Paper Internet,” Bartels Lecture at the University of Leeds, 2002.

Rayward, W. Boyd. 1994. Visions of Xanadu: Paul Otlet (1868-1944) and hypertext. Journal of the American Society for Information Science 45 (1994): 235-250.

Rayward, W. Boyd. 2002. “Anticipating the Digital World: Paul Otlet and his Paper Internet,” Bartels Lecture at the University of Leeds.

Universal Decimal Classification Consortium flyer.

Universal Decimal Classification Consortium, “About the UDC.” Resources

The Mundaneum, Mons, Belgium

Michael Buckland’s Paul Otlet page

Universal Decimal Classification Consortium Thanks

Thanks to Boyd Rayward, Francoise Levie and Stephanie Manfroid for their input and encouragement.

Images courtesy of the Mundaneum, centre d’archives, Mons, BelgiumAlex Wright is a writer, information architect, and former librarian who lives and works in San Francisco. He maintains a personal web site at

Alex Wright

Alex Wright is the author of Glut: Mastering Information Through the Ages. He currently works as an information architect for the New York Times.
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12 thoughts on “Forgotten Forefather: Paul Otlet”

  1. Alex,

    I happened to find this after reading your other article on Otlet from the New York Times ( thanks for shedding some light on such a visionary individual, especially in light of the current movement towards a semantic web.

    For the sake of conversation, here’s a link to the biographical documentary on Otlet hosted by the Internet Archive:


  2. Thanks for the article. I was surprised to learn of Otlet from a less-than-computer-involved friend. Astonished and pleased to learn of Otlet and his work, I made a set of links at my DMOZ bookmarks, here:,_Paul/
    The parent category, “Ontology,” includes a number of other links that may be of interest as well. In particular, I recommend the 2007 David Weinberger book, Everthing Is Miscellanous. One of his core concepts is “the third order of order,” which I can relate to the way Otlet saw that the concepts in books can relate to each other, a kind of foreshadowing of meta-tagging. I came to this book from correspondence with Clay Shirky, whose web page entitled “Ontology Is Overrated” I would also recommend highly.

  3. Incredible story. I wasn’t aware of Olet until a few weeks ago, I almost feel embarassed with him being such an important figure in the web.

  4. Thanks Alex! This is one of those articles I have always hoped someone would write. A fascinating man who deserves to be better remembered.

  5. What a fascinating article! How can I find out more about Paul Otlet? (Amazon only lists one book—International Organization and Dissemination of Knowledge: Selected Essays of Paul Otlet—and it’s out of print.)

  6. Very good article. I said that, if all people who make information architecture jobs seek intro Information Science deep, we going find many answers. Thanks Alex.

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