Hypermedia Fundamentals

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HypermediaFundamentals
Thanks to Carole Goble for slides

• What is hypermedia?
• Nodes and Links
• Hypermedia application characteristics
• Navigation and non-linear reading
• Hypermedia issues for the web

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What is Hypermedia?

• Hypertext a combination of natural language
  text with the computers capacity for branching,
  or dynamic display
• Ted Nelson, 1967
• Hypermedia multimedia hypertext. Hypermedia and
  hypertext tend to be used loosely in place of
  each other. Media other than text typically
  include graphics, sound and video.
• Hypertext Text which is not constrained to be
  linear
• World Wide Web consortium, Hypertext Terms,
  April 1995
• An application which uses associative
  relationships among information contained within
  multiple media data for the purpose of
  facilitating access to, and manipulation of, the
  information encapsulated by the data.
• Hypermedia and the Web , Lowe and Hall, 1999

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What is Hypermedia?

• Non-linear writing
• Interlinked texts
• Multiple pathways, multiple reading sequences
• Multiple media video, audio, images, emails,
  databases, spreadsheets
• Annotation and commentary
• Association of ideas
• Writing and reading not separated
• Interactive

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Nodes, Links and Anchors

• Node represents chunk of information
  corresponding to a natural semantic unit
• e.g. screen, page, frame
• The act of chunking information is part of
  authoring process
• Link represents an association between nodes
• Machine-supported fast inter-node connections
• Anchor represents a link on a node
• e.g. buttons, bolded text, hotspots, images
• the whole node might be an anchor but should be
  able to designate a sub-region as a source or
  destination of a link

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Hypermedia Linking

• Links are first class citizens
• Mechanics
• Single or multi- source / single or
  multi-destination
• Uni- / bi- directional
• Anchoring generic links, dynamic links
• Versioning Composites Virtual structures
• Computed Links (search and query on keywords or
  calculated from interests or trail so far)
• Annotation on Links
• Dynamic Links to running applications
• Link Context
• Maintenance
• Deletion Problem, dangling links, stranded nodes

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Link types

• Untyped links give too much freedom? links as
  GOTOs
• GUIDE hypertext system had
• Pop-up footnote links
• Replacement (fold-out) Hierarchic links
• Reference links for free associations
• Mouse cursor feedback on link type

• Semantic link types
• Subclass/superclass hierarchies
• Supports/opposes source node
• Is an example of source node
• Use
• Filter on type to cut down complexity
• Automatically process link types as part of an
  intelligent hypermedia application

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Taxonomy of semantic link types

• Normal Links
• Citation
• source, pioneer, credit, leads, eponym
• Background
• FutureWork
• Refutation
• Support
• Methodology
• Data
• Generalize
• Specialize
• Abstraction
• Example
• Formalization
• Application

• Commentary Links
• Comment
• critical, supportive
• RelatedWork
• misrepresents, vacuum, ignores, isSupersededBy,
  isRefutedBy, isSupportedBy, redundant
• ProblemPosing
• trivial, unimportant, impossible, ill-posed,
  solved, ambitious
• Thesis
• trivial, unimportant, irrelevant, redherring,
  contradict, dubious, counterexample, inelegant,
  simplistic, arbitrary, unmotivated
• Argumentation
• invalid, insufficient, immaterial, misleading,
  alternative, strawman
• Data
• inadequate, dubious, ignores, irrelevant,
  inapplicable, misinterpreted
• Style
• boring, unimaginative, incoherent, arrogant,
  rambling, awkward

• Argument
• deduction, induction, analogy, intuition
  solution
• Summarization
• Detail
• AlternateView
• Rewrite
• Explanation
• Simplification
• Complication
• Update
• Correction
• Continuation

http//www.eastgate.com/HypertextNow/archives/Trig
g.html
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Types of information

• Provide a form for the information space
• Allow user to develop an understanding of its
  scale and their location within the space
• Do not imply any semantic relationships between
  linked information

Structural links Organisational space

• Provides a link between an item of information
  and an elaboration or explanation of that
  information.
• The item at one end of a referential link exists
  because of the existence of the other item.
• E.g. a link from a word to its definition.

• Instantiation of a semantic relationship between
  information elements
• Links based meaning
• Cross referencing

Associative Referential links Information space
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Information Structures
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Info (Link) structures depend on

• CONTENT
• Material structure underlying
• Volatility of material
• Access paths
• CONTEXT
• How is it to be used?
• Who by?
• Where have they been before?

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Web hypermedia model

• Not developed in the context of a formal model of
  hypermedia
• Simple node-link model
• Links are simple
• Point to point
• Uni-directional
• Non-contextual
• Untyped
• Nodes are complex media compositions
• Browser frames improve contextualisation of
  info
• Java applets improve integration of media
• VRML, QT broaden range of media
• Plug ins improve browser functionality
• Link maintenance notoriously difficult
• dangling or obsolete links

gt Plugins to provide multi-destinations
gt Applications provide a map of
interrelationships
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Hypermedia issues for the Web

• Difficult to add own personal links to a WWW
  document without making a copy (and losing
  updates)
• Difficult to offer different link sets for
  different purposes
• eg Level I links, Level III links, my own links
• Difficult to provide computed links in a standard
  way dependent on some automatic computation
• Difficult to adaptively present web documents in
  different ways for different readers
• No standard non-proprietary support for
  hyperlinking between different desktop
  applications

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Hypermedia Application Goals

• To support (using the associative relationships
  between information sources) the carrying out of
  actions which
• result in the identification of
• facilitate the effective utilisation of
• result in control of
• appropriate information (with appropriateness
  being based on a given set of contextually
  defined criteria)
• Lowe and Hall, 1999
• Hampered or aided by hypermedia and presentation
  systems
• E.g. Web means you cant use generic links,
  multiple destination links, overlapping link
  anchors etc

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Hypermedia Application Characteristics

• Functional and non functional characteristics
• E.g. Follow a link from one page to another
• Expectation of navigation by browser
• FUNCTIONAL
• Expectation of relevance and correctness once
  link navigated
• NON FUNCTIONAL

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Functional Characteristics

• Navigability
• Orientation
• Information maps and overviews
• Information trails
• Information Contextualisation
• Searching and Indexing
• Document management
• Information Security and cost
• Presentation
• Customisability
• Effective use of resources
• Handling of temporal data

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Non functional Characteristics

• Link validity, correctness, relevance,
  completeness and integrity
• Content validity, correctness, relevance,
  completeness and integrity
• Content organisation
• Consistency and seamlessness
• Efficiency
• Maintainability and evolvability
• Reusability
• Reliability and Robustness
• Testability, validation and verification
• Interoperability, flexibility, portability,
  genericity
• Political and social aspects
• Cost effectiveness

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Hypermedia Navigation

• "Rhetoric of arrival and departure
• "The very existence of links in hypermedia
  conditions the reader to expect purposeful,
  important relations between linked materials
  ...... George Landow
• ... those documents that disappoint these
  expectations appear particularly incoherent and
  nonsignificant ..
• ... Books permit the student reader to avoid
  apparently nonsignificant or insignificant
  materials - one simply glances at them and turns
  the page .
• ... Hypermedia linking is a double-edged sword
  that offers readers information in new, more
  efficient ways but ... simple linking has
  capacity to confuse and leave readers ...

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Non-linear reading

• How are hypertext information systems different
  from traditional linear paper-based
  presentations (eg books) ?
• The rhetoric of arrival and departure - Landow
• Where am I?
• How do I get back to 5 screens ago?
• How do I get to XXX?
• What is the quickest way of getting to XXX?
• How can I find out more about this topic?
• What happens if I follow this link?
• How much information follows this link?
• Where have I come from?
• How do I get back?
• Who has been here before?
• MORE CONTEXT AND INFO ON LINKS

http//www.eastgate.com/
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Lost in Hyperspace (Conklin87)

• Problems of disorientation and navigation in
  large hyperspaces (Nielsen 1995 Multimedia and
  Hypertext)
• More reader/user choice
• Some control passed from author to reader
• but with greater choice comes
• more cognitive overhead
• Lost in Hyperspace problem
• Need for
• gt System-generated ways of orienting the reader
• Feedback of location (orientation cues)
• Effective navigation tools

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Navigation on the Web?

• Web has evolved some navigation tools
• conventional back links
• feedback on previously selected links
• bookmarks (but difficult to organise)
• history trail
• portals/link indexes
• rollover annotation on links gives some context
• popup annotation or basic URL address at bottom
• some interactivity
• But navigation is hampered by the poor link
  model, poor navigation instruments and poor
  design

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Navigation Context (1)
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Navigation and Context (2)
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Issues in hypermedia

• Location of information
• Primitive manual authoring of static links
• Users context
• Developing an understanding and responding
• Information contextualisation
• Support for
• intelligent browsing and navigation,
• information structuring,
• mechanisms for active annotation
• restructuring of networks based on feedback.

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Hypermedia issues for the Webreprise

• Difficult to add own personal links to a WWW
  document without making a copy (and losing
  updates)
• Difficult to offer different link sets for
  different purposes
• eg Level I links, Level III links, my own links
• Difficult to provide computed links in a standard
  way dependent on some automatic computation
• Difficult to adaptively present web documents in
  different ways for different readers
• No standard non-proprietary support for
  hyperlinking between different desktop
  applications

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Links are not first classreprise

• Links are embedded in the content
• No separate link database or link layer (hence
  XLink)
• Difficult to visualise all links separately or
  automatically process them
• Link maintenance notoriously difficult
• dangling or obsolete links

• We were awarded an excellent in lta href
  "http//www.qaa.ac.uk/revreps/subjrev/All/q235-94.
  htm"gt HEFCE's Teaching Quality Assessment
  exercise in 1994lt/agt.
• lta href"/Visitor_subweb/location.php3"gtPractical
  information for those visiting our buildingslt/agt

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Generations of Hypermedia Systems
Mainframe-based
Xanadu, Augment, Hypertext Editing System/FRESS,
ZOG/KMS
Intermedia, NoteCards, Hyperties KMS, Neptune,
Guide (OWL), HyperCard, Supercard, Microcosm,
Microsoft windows help system etc..
Workstation based PC-based
Standards and reference models Dexter
Hypertext on the internet WWW Hyper-G
Open Hypermedia Systems Microcosm, Webcosm, DeVise