and Motivation

Computers have primarily let us do calculations faster, or store bits more cheaply. Almost nowhere have they helped us improve or even maintain information's context, or handle its complexity.

Instead, limited by the need to keep discrete files and by hierarchical databases' demands for uniform information neatly boxed in defined fields, computer technology has provided us with useful tools...but tools that break and discard the context of the information. Only relatively recently has windowing technology finally given us one of the simplest of paper's attributes: the ability to keep context by having two or three pieces of paper on your desk at the same time.

John Muir observed that "When we try to pick out anything by itself, we find it hitched to everything else in the universe." Hypertext is software that helps us keep ideas hitched together in ways that better represent reality.

In paper-based reading and writing, we have evolved a valuable set of traditions to provide context for information. A page of a book has quotations and citations which tell about antecedents, or about the intellectual context which helped shape the author's thoughts. We see marginalia and footnotes adding bits of intriguing information or exploring paths that diverge from the main thrust of the argument. In library books we occasionally see a scribbled note vehemently affirming or disparaging the text. Each one of these connections or associations on the page is a link: linking the writing to some reader's pungent opinion, or to collateral or source material sitting on some other shelf in some other library. But beyond the pages of the books are other comments connected by invisible links: book reviews, catalogues and guides listing our book, and new books with footnotes that list our book as a source. Imagine each of these links connected by a thread to form a physical trace of complex web of context. Hypertext software lets us weave that web.

Xanadu & Udanax

Xanadu began in 1960 with Ted Nelson's simple definition of hypertext as "non-sequential writing": text that branches and allows choices to the reader. The demands on the design have expanded since then, and our understanding of fundamental issues has deepened as well. These philosophies and motivations drove the technical design of the Udanax. They explain: * some of our unusual technical choices

* our intent in creating a particular capability

* the sometimes surprising absence of features standard in other software
Importance of Context and Complexity

The basis of Udanax hypertext's design is that information is complex, and all information is embedded in a context that gives it meaning. The common misconception is that things are meaningful by themselves, i.e., that a word has an atomic definition or that documents are self-contained bodies of meaning. Instead, meaning requires a topology of relationships. Words and documents gain their full meaning because of their relationships to other words, documents, ideas, and circumstances.

Computer science has concentrated on better representing the document content rather than the context; current text systems are built around the idea of documents as islands. But the meaning to be extracted from a document still depends on a person's ability to know the context of a situation. If a person does not already know the document's significance as it relates to the background of controversies or evolving knowledge, he will not understand its critical points.

With current technology, pieces of information are destroyed, get lost or are stored but never found by the people who most need them. Libraries burn, files are misplaced in cabinets, or a piece of knowledge is simply lost in the growing sea of information. Take the notion of a theory and a refutation. The two ideas are separated by space, time, authorship, perhaps even disciplines. The refutation may be undiscovered and undiscoverable by a researcher, who then wastes years of effort pursuing an erroneous idea. If theory and refutation could be permanently linked together, the web of context would be vastly enriched.

In other areas of human information finding and sharing - decisionmaking, consensus-building, debate and argumentation - we handle large and complex chains of arguments in an even more haphazard fashion. For these uses, too, we very much need ways to preserve context, and to build webs of relationship where no technology now exists to do so.

A Medium for Multimedia

Information exists in a variety of forms and formats: text, film, music, graphics, charts and more. Varied as the formats might be, the information content is intensely intertwined. Without a single medium to represent the range of forms or the interconnections, you must break up the information into units your technology can manage. Our inability to deal with diversity plagues us. We divide knowledge into different academic disciplines. We build and run on incompatible machines. We store our information in different formats, and we use incompatible software tools.

To overcome this problem, a system must contain all types of information. And, to be effective, the system must have virtually no limit on the quantity of interconnected information it can support. Udanax Green can support this limitless interconnection.

The Value of Diversity

Another key philosophical building block for us is the value of diversity, the richness that comes from pluralism and freedom of choice. In new and complex situations the right answer is never known at the outset; we move progressively closer to a good answer through the interaction of diverse opinion. Where diversity of opinion and knowledge are supported, human decisions are richest and come fastest. Knowledge is accrued slowly over time; where knowledge can be preserved and kept a part of the ongoing discussion, we save reliving old mistakes.

At its simplest, hypertext capitalizes on diversity's robustness in the multiple paths leading to any piece of information; in contrast, hierarchical systems are built on the assumption that all people will follow the same path to find a piece of information even if they need that information for different reasons. In addition, non-sequential reading empowers readers to follow the path of greatest interest, rather than the single road laid out by an author of a linear text.

But hypertext also addresses the problems that arise with the fragmentation of knowledge. The social interaction that hypertext supports allows maximum diversity to coexist and cross-fertilize.