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Hypertext at its simplest level is the ability to create linkages between pieces of text. The start of a link may be delineated in some ways (such as underlining) to indicate the availability of a link. The destination (or target) of a link is not normally so delineated. Activating the link (usually by clicking on it with a mouse, perhaps at the same time holding a special key on the keyboard) 'jumps' the reader to the destination and displays the text found there. The term hypertext was first coined by Theodore Holm (Ted) Nelson in 1965 [Nelson, 1965]. The ideas underlying hypertext can be traced back perhaps as far as the earliest Hebrew citation indexes [Weinberg, 1997] with manual hypertext/hypermedia implementations being available as early as 1907 [Rayward, 1994], [Rayward, 1997].
Hypertexts are usually made up of more than one node. These are semi-autonomous pieces of text that are connected together and navigated through by means of hypertext links. Links can also connect pieces of text within nodes. For instance, a journal article structured as a single hypertext node might have a table of contents at the start where each entry was a link to that section of the article. Such internal links are usually less common than external links to other nodes.
This simple model of hypertext links can be enriched by adding link directionality, multiple destinations and link typing. A wide range of link types are possible [Grabinger et al., 1992a], [Grabinger et al., 1992b], [Grabinger et al., 1993a], [Grabinger et al., 1993b]. With link directionality, hypertext links can be either uni- or bidirectional. Some hypertext systems, such as the World Wide Web support unidirectional links only. The usual corollary of unidirectional links is that they cannot be traversed 'backwards' from destination to source. This means that it is impossible to see which links point to a particular node. Such information is very useful if one wishes to know how many times a hypertext article is 'cited' or if one wishes to move a node and notify all the links pointing to it of the new destination. Multiple destinations allows a single link to point to multiple destinations and for the user to select which link they traverse. Link typing enables the designer of hypertexts to characterise links according to a predefined set of types. These might be rhetorical classifications: 'comment', 'amplification', 'refutation', and so on [Landow, 1989]. They might also be type of linked data: movie, sound file, Word document, and the like. None of these enrichments are currently supported by the World-Wide Web.
Last modified: Monday, 11-Dec-2017 14:39:25 AEDT
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