Some questions of hypermedia and CHI

1. Some questions of hypermedia and CHI Josep Blat Universitat Pompeu Fabra

2. 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

3. 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)

4. 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

5. 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

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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

13. 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.