Human-computer interaction: users, tasks & designs User modelling in user-centred system design (UCSD) Use with Human Computer Interaction by Serengul Smith-Atakan ISBN © 2006 Middlesex University Press

By the end of this lecture you should... Understand what ‘guidelines’ are, and why they are important –Be able to distinguish between ‘principles’, ‘design rules’ and ‘standards’ –Where they come from –Where and when to use them Be familiar with several important design principles Use with Human Computer Interaction by Serengul Smith-Atakan ISBN © 2006 Middlesex University Press

By the end of this lecture you should... Describe various ways of creating user models Be aware of Nielsen’s heuristics and how they can be used to evaluate interactive systems Use with Human Computer Interaction by Serengul Smith-Atakan ISBN © 2006 Middlesex University Press

Types of user model Psychological theories as user models Task analysis for user models Cut-down psychological theories as user models Simplistic psychological theories as user models Simplex One as a simplistic theory Use with Human Computer Interaction by Serengul Smith-Atakan ISBN © 2006 Middlesex University Press

User models and evaluation Using design principles or heuristics for evaluation Evaluating user requirements with Simplex One Evaluating design options with Simplex One Use with Human Computer Interaction by Serengul Smith-Atakan ISBN © 2006 Middlesex University Press

Simplex One A key feature of this model is that each cognitive module can take input from any other module in the system via the executive function. Use with Human Computer Interaction by Serengul Smith-Atakan ISBN © 2006 Middlesex University Press

Evaluating design options with Simplex 1.Sensory and Perceptual Zone Does the system provide adequate visual, auditory or other modality input to people using it? Are the immediate sensory memory requirements of the system too much? 2. Output Zone Does the system require reasonable responses from users? Does the system provide adequate response support? 3. Abstract Working Zone Does the system place too many demands on working memory? Do the people who use the system have the necessary working memory capabilities? Use with Human Computer Interaction by Serengul Smith-Atakan ISBN © 2006 Middlesex University Press

Evaluating design options with Simplex 4. Long Term Data Warehouse Does the system require the long term memory to hold too much information? Does the system support long term learning when necessary? Do the people who use this system have the necessary memory skills? 5. Executive Functions Zone Does the design require too many or too complex operations? Does the design require a level of task coordination which is too detailed to learn easily? Does the design make it very difficult to track and monitor current progress in tasks? Use with Human Computer Interaction by Serengul Smith-Atakan ISBN © 2006 Middlesex University Press

Guidelines... Principles Design rulesStandards Guidelines Use with Human Computer Interaction by Serengul Smith-Atakan ISBN © 2006 Middlesex University Press

Principles vs design rules A principle is a high level and widely applicable guideline Design rules are principles that have been interpreted for a particular design. They are narrow, focused, practical and specific Use with Human Computer Interaction by Serengul Smith-Atakan ISBN © 2006 Middlesex University Press

Examples... Principles –Know the user population –Reduce cognitive load –Engineer for errors –Maintain consistency and clarity Design rules –always position the waste bin in the bottom right hand corner –always issue a warning before the user deletes a file Use with Human Computer Interaction by Serengul Smith-Atakan ISBN © 2006 Middlesex University Press

Design rule or principle? How many ways can a guideline be interpreted? –‘always position the waste bin in the bottom right hand corner’ –can only be interpreted one way, therefore design rule –‘be consistent’ –can be interpreted lots of ways, therefore principle Use with Human Computer Interaction by Serengul Smith-Atakan ISBN © 2006 Middlesex University Press

Principles become design rules Principles and design rules are not entirely separable things There should be a path from a principle to a design rule In other words: –Principles are intended to be general –When they are interpreted for a specific design they become design rules Use with Human Computer Interaction by Serengul Smith-Atakan ISBN © 2006 Middlesex University Press

A continuum... PrinciplesDesign rules General Widely applicable ‘Theoretical’ Specific Narrow application Practical Use with Human Computer Interaction by Serengul Smith-Atakan ISBN © 2006 Middlesex University Press

Standards A standard is a guideline with a high level of authority Typically standards must be applied to a design Standards may be ‘in house’ Standards may legally enforced Use with Human Computer Interaction by Serengul Smith-Atakan ISBN © 2006 Middlesex University Press

Standards It has to be definite when (or not) a standard has been applied Therefore a standard tends to be a design guideline It is difficult to enforce something if it has multiple interpretations –(Unless you want to make lots of money for lawyers) Use with Human Computer Interaction by Serengul Smith-Atakan ISBN © 2006 Middlesex University Press

Where do guidelines come from Practical experience –Nielsen’s guidelines are based on his practical experience in designing interactive systems Psychological theory –Theories of how people behave inform ideas about how to design usable systems Use with Human Computer Interaction by Serengul Smith-Atakan ISBN © 2006 Middlesex University Press

Well-known design principles Learnability Flexibility Predictability Consistency Recoverability Responsiveness Use with Human Computer Interaction by Serengul Smith-Atakan ISBN © 2006 Middlesex University Press

Nielsen’s heuristics Visibility of system status Match between system and the real world User control and freedom Consistency and standards Error prevention Recognition rather than recall Flexibility and efficiency of use Aesthetic and minimalist design Help users recognise, diagnose, and recover from errors Help and documentation Use with Human Computer Interaction by Serengul Smith-Atakan ISBN © 2006 Middlesex University Press

Summary Guidelines characterise aspects of “good design” Can be used to aid design process Come in different forms –Guidelines, Principles, Rules, Standards –Vary in generality and authority –require different degrees of interpretation Use with Human Computer Interaction by Serengul Smith-Atakan ISBN © 2006 Middlesex University Press