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Multimedia

Hypertext and Hypermedia

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Hypertext Issues

• Hypertext History

• Hypertext Representation

• Application Example (Nielsen)

• Hypertext Navigation Aids

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Normal Text vs. Hypertext

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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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Envisioned Memex

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Linearity vs. Non-linearity

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Hypertext View

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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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Hypermedia

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Hypermedia View

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A Web site is Hypermedia

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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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Various destination anchors

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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]

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Dexter Model (88-90)

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Flag Model (HT’96)