Hypertext and hypermedia

Most computer users today are familiar with the concept of hypertext, even if they don’t often use the term itself. Each time a Web user clicks on a link on a Web page, he or she is using hypertext. Most on-line help systems also use hypertext to take the reader from one topic to another, related topic. The term hypermedia acknowledges modern systems’ use of many kinds of resources other than plain text, including still images, videos, and sound recordings.

In a traditional document, the reader is generally assumed to proceed sequentially from the beginning to the end. (Although there may well be footnotes or cross-refer-ences within the document, these are generally experienced as temporary divergences from the primary, sequential nar-rative.) Generally speaking, each reader might be expected to acquire roughly the same set of facts from the document.

In a hypertext document, however, the links between topics create multiple potential paths for readers. To the extent the author has provided links between all related topics, the reader is free to pursue his or her particular interests rather than being bound by a sequential structure imposed by the author. For example, in a document that discusses various organisms in an ecology and the effects of climate and vegetation, one reader might choose to explore one organism in depth, following links from it to other resources devoted to that organism (including outside Web pages, images, videos, and so on). Another reader might be interested specifically in the effects of rainfall on the ecol-ogy as a whole and follow a completely different set of links to sites having climatological data.

History and Development

In 1945, a time when the very first digital computers were coming on-line, Vannevar Bush, a pioneer designer of ana-log computers, proposed a mechanism he called the Memex (see Bush, Vannevar). This system would link portions of documents to allow retrieval of related information. The proposal was impracticable in terms of the very limited capacity of computers of the time. By the 1960s, when com-puters had become more powerful (and the minicomputer was beginning to be a feasible purchase for libraries and schools), another visionary, Theodore Nelson, coined the terms hypertext and hypermedia. He suggested that net-working (a technology then in its infancy) could allow for what would eventually amount to a worldwide database of interconnected information. Nelson developed his specifi-cations for a system he called Xanadu, but he was unable to create a working version of the system until the late 1990s. However, in 1968 Douglas Engelbart (also known as the inventor of the computer mouse) demonstrated a more lim-ited but workable hypertext system called NLS/Augment.

During the 1970s and 1980s, a variety of hypertext sys-tems were created for various platforms, including Guide and Toolbook for MS-DOS and Windows PCs. Perhaps the most influential system was Hypercard, developed for Apple’s Macintosh. While Hypercard did not have a com-plete set of facilities for creating hypertext, the flexible, programmable, linkable “cards” could be used to imple-ment hypertext documents. Many encyclopedias and other reference products on CD-ROM began to implement some form of hypertext links.

The true explosion of hypertext came with the develop-ment and growth of the World Wide Web throughout the 1990s. Hypertext on the Web is implemented through the use of HTTP (HyperText Transport Protocol) over the Inter-net’s TCP/IP protocol and by coding documents in HTML (Hypertext Markup Language). (See html, Internet, tcp/ ip, and World Wide Web.)

Implementation

A hypertext document consists of nodes. A node can be a part of a document that conveys a logical “chunk” of infor-mation, such as the text that would be under a particular heading in a traditional document. In some systems nodes can be grouped together as a composite—for example, the second-level headings under a first-level heading might be considered nodes making up a single composite.

The text contains links. A link specifies an anchor or specific location to which it points. The user normally doesn’t see the anchor, but rather the marker, which is some form of highlighting (such as a different color) that indicates that an area is a link that can be clicked on. (In systems such as the Web, link markers need not be textual. Small pictures are often used as visual link mark-ers.) Web browsers and other hypertext programs often supplement the use of links with various navigation aids. These can include buttons for traversing back or forward through a list of recently visited links, a history list from which previous links can be selected, and bookmarks that allow the user to save and descriptively label important links for easier future access.

Hypertext is becoming the dominant paradigm for pre-senting technical or other reference information. With less-structured text, hypertext links are usually considered to be supplemental to the traditional structure. The term hyper-media refers to the linking of nontextual material—images, videos, sound files, even Java applets and other programs. (Since both hypertext and hypermedia are now so ubiquitous, the terms themselves seem to be used less frequently except in an academic context.)

Hypertext perhaps achieves its fullest power when it is used for collaborative expression and research. Without being able to easily link to what is being discussed, blogs would just be static diaries (see blogs and blogging). Wikis, too, depend on linking not only to reference exist-ing, related entries, but to “grow” the tree of knowledge with “stubs” being put in to encourage other contributors to flesh out related topics (see wikis and Wikipedia). Despite suggestions to the contrary, hypertext seems to be problem-atic with regard to fiction, unless a work is constructed as an explicit hypertext. If hypertext literature becomes popu-lar, it will require that both authors and readers radically change their role and expectations with regard to the text.