Existing Automatic Linking Systems

The goal of using hypertext to accelerate on-line education is not new, and many systems have been developed over the past decades. However, we are aware of no pre-existing systems that satisfy all of the following requirements:

• freely available
• downloadable (e.g., to support automatic link installation)
• open such that anyone can contribute their knowledge
• accommodates competing sources of information
• provides one or more ranking systems for arbitrating competing definitions
• supports alternative wordings and phrasings (for automatic link installation)

While there are many on-line dictionaries available, there appear to be none designed to support automatic linking. There are some tools for automatic linking, however, which are based on proprietary closed dictionaries:

• GuruNet
• QuickClick
• Microsoft Smart Tags

These systems all have great merit, but they serve the much less ambitious goal of automating a closed collection of links, typically to a conventional dictionary which has been ported to on-line form. The solution we seek, on the other hand, is more general in several ways:

• We wish to link arbitrarily long phrases naming any topic, as opposed to the single words and short phrases found in most dictionaries. For example, in a scientific education context, home pages are needed for every fundamental topic, such as ``first law of thermodynamics'' and ``conservation of momentum''. We also need to accommodate alternate phrasings, such as ``momentum conservation''.

• Educators need to be able to expand the dictionary as needed. No closed product can keep up with advancing nomenclature in all fields, especially in more technical areas.

• A natural consequence of expandability is competition. Competing definitions should be accommodated, with some means for ranking them according to quality.

• Instead of the short definition typical of a dictionary entry, we prefer an entire home page providing a top-down clearing house for all known best information on the topic. A good topic home page will include a dictionary style definition, but also a general introduction and overview, plus links to encyclopedia articles, other tutorials, books, related topics, and so on. We are no longer limited by book size and/or cost, and the Web is spontaneously producing excellent definition home pages.

• The dictionary should be organized according to context so that alternate meanings can be eliminated by specifying context. In particular, a given word or phrase can be formally assigned to the highest level context in which its meaning is unique. Conversely, when a new meaning appears for a particular word or phrase, its level can be moved down in the context hierarchy accordingly.

• The author must have the option of complete control over all automatic links, including the ability to conveniently override or delete any link. One way to ensure this is to explicitly install links in on-line documents, as opposed to automating them in a browser à la Atomica, QuickClick, and Smart Tags. Explicitly installed links can be carefully selected and reviewed by the author.

The relation of the Open Dictionary to other related websites is given in Appendix .