Gary MarsdenSlide 1University of Cape Town Human-Computer Interaction - 7 Design Guidelines & Standards Gary Marsden ( ) July 2002

Gary MarsdenSlide 2University of Cape Town Unit Objectives  We shall cover –Design guides –What they look like –Perils of using them  Rationale: –It is impossible for designers to be expert in all the disciplines of HCI, so guidelines are constructed to guide non-experts in matters such as psychology, art, sociology etc.

Gary MarsdenSlide 3University of Cape Town Standards  We have already looked at standards as a reason for the inclusion of user needs in software projects  The question remains if it is possible to use standards to generate usable systems –i.e. could a programmer follow some usability standard to produce an easy to use system?

Gary MarsdenSlide 4University of Cape Town Authority  We first need to distinguish between standards and guidelines –Guidelines are more interesting as they embody results from say psychology or sociology without requiring the designer to understand the underlying theory

Gary MarsdenSlide 5University of Cape Town Standards  set by national or international bodies to ensure compliance by a large community of designers  standards require sound underlying theory and  slowly changing technology  hardware standards more common than  software  high authority and low level of detail  ISO 9241 defines usability as effectiveness,  efficiency and satisfaction with which users  accomplish tasks

Gary MarsdenSlide 6University of Cape Town Guidelines  more suggestive and general  many textbooks and reports full of guidelines  abstract guidelines (principles) applicable  during early life cycle activities  detailed guidelines (style guides) applicable  during later life cycle activities  understanding justification for guidelines aids in  resolving conflicts

Gary MarsdenSlide 7University of Cape Town Catch  Of course, nothing is that simple  The more general a design rule, the more it is likely to conflict with other rules –To resolve this, it is necessary to understand the underlying theory  We shall now look at the types of design rules and principles available

Gary MarsdenSlide 8University of Cape Town Design Principles  Learnability –the ease with which new users can begin effective interaction and achieve maximal performance  Flexibility –the multiplicity of ways the user and system exchange information  Robustness –the level of support provided the user in determining successful achievement and assessment of goal-directed behaviour

Gary MarsdenSlide 9University of Cape Town Learnability  Predictability –determining effect of future actions based on past interaction –history operation visibility  Synthesizability –assessing the effect of past actions – immediate vs. eventual honesty  Familiarity –how prior knowledge applies to new system –guessability; affordance  Generalizability –extending specific interaction knowledge to new situations  Consistency –likeness in input/output behaviour arising from similar situations or task objectives

Gary MarsdenSlide 10University of Cape Town Flexibility  Dialogue initiative –freedom from system imposed constraints on input dialogue –system vs. user pre-emptiveness  Multithreading –ability of system to support user interaction for more than one task at a time –concurrent vs. interleaving; multimodality  Task migratability –passing task execution between user and system  Substitutivity –allowing equivalent values of input and output to be substituted for each other –representation multiplicity; equal opportunity  Customizability –modifiability of the user interface by user (adaptability) or system (adaptivity)

Gary MarsdenSlide 11University of Cape Town Robustness  Observability –ability of user to evaluate the internal state of the system from its perceivable representation –browsability; defaults; reachability; persistence; operation visibility  Recoverability –ability of user to take corrective action once an error has been recognized –reachability; forward/backward recovery; commensurate effort  Responsiveness –how the user perceives the rate of communication with the system  Task conformance –degree to which system services support all of the user's tasks –task completeness; task adequacy

Gary MarsdenSlide 12University of Cape Town The problem with the classic ‘7  2’  George Miller’s theory of how much information people can remember  People’s immediate memory capacity is very limited  Many designers have been led to believe that this is useful finding for interaction design

Gary MarsdenSlide 13University of Cape Town What some designers get up to  Present only 7 options on a menu  Display only 7 icons on a tool bar  Have no more than 7 bullets in a list  Place only 7 items on a pull down menu  Place only 7 tabs on the top of a website page –But this is wrong? Why?

Gary MarsdenSlide 14University of Cape Town Why?  Inappropriate application of the theory  People can scan lists of bullets, tabs, menu items till they see the one they want  They don’t have to recall them from memory having only briefly heard or seen them  Sometimes a small number of items is good design  But it depends on task and available screen estate

Gary MarsdenSlide 15University of Cape Town Other Guides  There are many, many more guides out there –Education, research, government, manufacturer  All have some value, but make sure you are using the most appropriate ones  If it goes against your intuition, there is nothing for it but user testing

Gary MarsdenSlide 16University of Cape Town Summary  In this section we looked at –Different sorts of guides that may be used to create better interfaces –An example design guide, with three main sections of principles Learnability, flexibility and robustness –The perils of using guidelines blindly