Some questions of hypermedia and CHI

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Some questions of hypermedia and CHI

• Josep Blat
• Universitat Pompeu Fabra

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Some aspects of human-computer interaction and
hypermedia

• General question Human information processing
  based models (GOMS, for example)
• Experimental evaluation is a must
• Complexity of developing successful hypermedia

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GOMS, Human Information Processing

• GOMS (Card, Moran, Newell) stands for Goals,
  Operators, Methods, Selection rules
• GOMS tries to predict performance (and usability
  problems) when using computer systems
• Based on an Applied Psychology model of the Human
  Information Processor
• The HIP is composed of perceptual, motor and
  cognitive systems (and corresponding perceptual
  and cognitive memories, which can be short term
  or long term)

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Example of GOMS application

• The keystroke level model based on GOMS tries to
  predict performance when using a text editing
  system
• Methods for this model are keystroking, pointing
  with a mouse, returning the hands to home,
  drawing a specific line, mental preparation,
  response by system
• Operators in this model are sequences of methods
  allowing to perform a small unit-task

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Example of GOMS application 2

• Parameters can be estimated and performance
  predicted using some laws
• For instance, Fitts law for time T required to
  point with the mouse depends on size S of the
  object, of distance D as T 1.03 .096 log
  (D/S.5) it is based on the model of HIP
• Constants were experimentally obtained
• Experimental validation of predictions can be
  carried out

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More general GOMS analysis

• Hierarchical decomposition and analysis of tasks
  can be performed, in general, using GOMS at
  different levels of granularity
• We can compare different interfaces when
  performing specific tasks (or alternative methods
  which can be selected when using an interface)
• There are other models refining this one, and
  taking into account semantic, and syntactic
  aspects allowing for analysis of interfaces

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Concluding about GOMS

• Use Applied Psychology models of human
  information processing
• Develop task analysis, and performance models
• Predict and evaluate (time) performance
• GOMS is a relevant model

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Experimental evaluation

• Under GOMS, experiments can be used to evaluate
  prediction (and hence, predict performance)
• General experimental evaluation is a must for a
  user-oriented approach
• Example Evaluating experimentally whether
  hypertext browsing is better than using standard
  (paper based) documentation

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Evaluating hypertext vs traditional documentation

• Ask specific items for evaluation such as
• Searching fixed questions
• Writing essays
• Recalling incidental information
• Also ask about subjective rating

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Evaluating hypertext vs traditional documentation
2

• Experimental results (1989) using Superbook
  showed superiority
• In accuracy when searching three out of four
  fixed questions, especially when questions not
  clearly in documentation headings,
• When writing open book essays by students
• Recalling some incidental information
• Subjective rating gave also advantage to
  Superbook
• Seemingly, hypertext allows for better
  performance in non-standard cases

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Concluding about experimental evaluation of
hypertext

• Experimental evaluation is a must for
  user-centred approach
• Evaluation must be done with precise questions
• But also subjective rating is interesting
• Understand hypertext advantages with respect to
  text

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Seven barriers to successful hypermedia
development

• Glushko (1992) quotes seven pitfalls
• Realistic expectations
• Multidisciplinary project team
• Establishing and following design guidelines
• Dealing with installed base constraints
• Obtaining usable source files
• Finding appropriate software technologies and
  methods
• Legal uncertainties wrt intellectual property
  concerns
• Good commercial hypertext is hard to develop

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Some references

• Ronald M Baecker et al Readings in
  Human-Computer Interaction (Toward the Year
  2000), Morgan Kauffman, 1995. Chapters 9 and 13.
• Stuart K. Card, Thomas P. Moran, Allen Newell
  The Psychology of Human-Computer Interaction,
  Lawrence Erlbaum Associates, 1983.