Post on 21-Dec-2015
transcript
T.Sharon-A.Frank
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Hypertext Issues
• Hypertext History
• Hypertext Representation
• Application Example (Nielsen)
• Hypertext Navigation Aids
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Hypertext
• Text augmented with links:– Link: pointer to another piece of text in same
or different document.
– Navigational metaphorUser follows a link from its source to its
destination, usually by clicking on source with the mouse.
– Use browser to view and navigate hypertext.
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• Memex – Vannevar Bush, 1945– Concept of linked documents; photo-mechanical realization never implemented.
• Xanadu – Ted Nelson, late 1960s onwards– Hypertext defined; intended as global system but no real popular implementation.
• Hypercard – Apple, 1987– Shipped with every Mac; popularized concept.
• World Wide Web – 1993
Glimpse into Hypertext History
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MEMEX
• MEMEX – MEMory EXtender
by Vannevar Bush– Developed 1932
– Publication 1945
– Great Insights
– Never implemented
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• Hypertext is not usually read linearly (from start to finish).
• Links encourage branching off.
• History and back button permit backtracking.
• Not an innovation, but the immediacy of following links by clicking creates a different experience from traditional non-linearity (e.g. cross-references in encyclopedia).
Non-linearity
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Hypertext/media structure is a graph
Nodes – Information Units
Edges – Links to other Information Units
Navigation: traversing through the graph
Source Destination
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Graph is Media Independent
• Text• Graphics• Still Images• Audio• Animation• Motion Video ABC
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• Simple unidirectional links:– Connect single point on one page with a point on another page (e.g. Web).
• Extended links:– Regional links (ends may be regions within a page).– Bidirectional links (may be followed in both directions).– Multi links (may have more than two ends).
Types of Links
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Hypertext Abstract Machine (HAM)
Presentation Level
Hypertext Abstract Machine (HAM) Level
Host File Systems Level
[Campbell & Goodman, 1988]