Linking Systems:
According to Landow (1997), the link is the element that hypertext adds to reading and writing and Landow describes the various forms of linking as;
1. Unidirectional lexia to lexia: 
Advantage: simple, requires little planning.
Disadvantage: disorients when used with long documents, since readers
do not know where the link leads; best used for brief lexias or in systems
that use card metaphor.
2. Bidirectional lexia to lexia: 
Advantage: by permitting readers to retrace their steps creates simple
but effective means of orientation. Particularly helpful when arriving at
lexias that have only one or two departure links.
3. String (word or phrase) to Lexia: 
Advantages: (1) allows simple means of orienting readers; (2) permits
longer lexias; (3) encourages different kinds of annotation and linking
Disadvantage: disorients when used with long documents, since readers
do not know where link leads; best used for brief lexias or in systems that
use card metaphor.
4. String to String: 
Advantage: permits clearest way to end links.
Disadvantage: requires more planning than do links to full lexias.
5. One-to-Many: 
Advantages: (1) encourages branching and consequent reader choice;
(2) permits efficient author-generated overview and directory documents; (3)
when combined with systems that provide link menus and other preview functions,
helps greatly in orienting readers.
Disadvantage: can produce sense of atomized text.
6. Many-to-One Linking: 
Advantages: (1) handy for glossary functions or for texts that make
multiple references to a single text, table, image, or other data; (2) encourages
efficient reuse of important information; (3) allows simple means of producing
documents for readers with differing levels of expertise.
Disadvantage: systems that create many-to-one linking automatically
can produce a distracting number of identical links.
7. Typed links: 
Advantages: (1) if clearly labeled, acts as a form
of link preview and aids reader comfort; (2) can produce different kinds of
link behaviour, including pop-up windows.
Disadvantage: can clutter reading area or confuse by producing too
many different actions when one follows links.[1]
With
so many different types of linking systems available to the writer a diagram
of a typical hypertext novel could easily be
represented thus: (click on thumbnail for larger
image)
Site map for this hyper-narrative: (click on
thumbnail for larger image)
It would appear as if the concept that Ted Nelson planned for hypertext has been achieved. However, Nelson does not agree.
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[1] In Landow, G. 1997, Hypertext 2.0: The Convergence of Contemporary Critical Theory and Technology, The John Hopkins University Press, London, pp 12-15. back
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References:
Landow, G. 1997, Hypertext 2.0: The Convergence of Contemporary Critical Theory and Technology, The John Hopkins University Press, London.