Today’s class Group Presentation More about principles, guidelines, style guides and standards In-class exercises More about usability Norman’s model of.
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Today’s class Group Presentation More about principles, guidelines, style guides and standards In-class exercises More about usability Norman’s model of interaction Interaction components
Principles of Software Usability ( by Jakob Nielson and Rolf Molic) Simple and natural dialog. (Dialogs should not have any irrelevant or infrequently used information. All information should be arranged in a way that is natural to users. ) Speak the user’s language. (Dialogs should be expressed in text and concepts familiar to users.) Minimize user memory load. (Users should not have to remember information as they move from one part of the dialog to another. ) Consistency. (Users should not have to wonder whether different words, situations, or actions mean the same thing. ) Feedback (Users should always be informed about what is happening in the system.) Clearly marked exists. (System should have visible exits so that users can leave any unwanted situation.)
Principles of Software Usability ( by Jakob Nielson and Rolf Molic) Shortcuts. (Accelerators that speed up tasks should be available for expert users.) Good error messages. (Messages should, in plain language, state the problem and suggest a solution.) Prevent errors. (Systems should, whenever possible, prevent problems from occurring.) Help and documentation. (Information should be easy to retrieve and should list required steps to complete tasks.)
Shneiderman’s Eight Golden Rules for Dialogue Design Consistency (Consistent sequences of actions should be used in similar situations; Identical terminology should be used in menus, prompts and help screens; Commands should operate in a consistent manner Very often violated) Provide shortcuts (As users become experts they want to reduce number of interactions and increase pace. Should allow abbreviations, accelerator keys, hidden commands, extra options) Offer informative feedback (For every action there should be some feedback. For frequent, minor actions maybe simple feedback for infrequent major actions more demanding.) Design dialogues to yield closure (Sequences of actions should be organised into groups. Feedback can then be given at the end of a sequence to indicate it is over. User can then move on to next task) Simple error handling (Design system to avoid errors happening. If error occurs system should detect this, indicate it in an understandable way and provide simple mechanisms for recovery. User should not have to retype a whole command, just fix the incorrect part.)
Shneiderman’s Eight Golden Rules for Dialogue Design Permit easy reversal of actions (Actions should be reversible. This will relieve anxiety since user knows that errors can be undone; encourages exploration. This can be done with an undo command, this may undo last action, last group of actions, or more what about irreversible actions?) Support internal locus of control (Users should feel they are in control. Surprising system actions, tedious sequences of data entry or difficulty in obtaining necessary information increase anxiety. Users should initiate actions.) Reduce short-term memory load (Limit of STM is 7±2 items. Keep displays simple, avoid multiple page displays where must remember items from one to the next. Allow sufficient training time to learn codes, mnemonics and sequences of actions.)
Role of Principles and Guidelines Raising awareness of concepts Assisting in design choices Offering strategies for problem solving Supporting evaluation *There is no easy ‘cookbook’ solution to designing interfaces, even harder to design good multimedia interfaces.
Problems with Principles Principles must be interpreted, refined and extended for the particular environment. Must be interpreted in context of use. Because of this can be applied wrongly. Skills are required to use them effectively
Principles and Guidelines in the Iterative Design Process Evaluating a design using principles and guidelines Any contraventions can be spotted and corrected before the design goes any further
Web Design Guidelines It makes the web page user interface designer think carefully about the page layout and structure Top Ten Mistakes in Web Design by Jakob Nielsen’s http://www.useit.com/alertbox/991003.html Check out these web-sites for more guidelines: http://usableweb.com/ http://itserver.footscray.vic.edu.au/it/webdesign/
Style Guides Describe how to design interface ‘look and feel’ for a particular environment. Enables consistency between applications within one environment. All major systems have them.
Apple & Microsoft Look Figure 1 – different icons and messages. What is the main difference between the Microsoft messages and the Apple Macintosh versions?
Standards Set by national and international bodies H/W standards based on ergonomics, physiology, etc. S/W standards less common as system design less well understood International standards for user interface design slowly emerging ISO 9241 is an HCI standard ISO9241-10-17 deal with software aspects of display design, keyboard requirements, user guidance, etc
References HCI by Jenny Preece HCI information by Steve Brewster Designing Web Interfaces by Michael Rees User-centered information design for improved usability by Pradeep Henry