User Interface Design

1. User Interface Design CIS 375 Bruce R. Maxim UM-Dearborn

2. Principles of Good Design • State and action alternatives are visible • Conceptual model is consistent with system image • Interface should include mappings that reveal relationships among task stages • User should receive continuous feedback

3. 8 Golden Rules of User Interface Design • Strive for consistency • Enable short-cuts for frequent users • Informative feedback • Design dialogs to yield closure • Offer simple error handling • Permit easy reversal of actions • Support internal locus of control • Reduce short-term memory load on user

4. Place User in Control • Define interaction in such a way that the user is not forced into performing unnecessary or undesired actions • Provide for flexible interaction (users have varying preferences) • Allow user interaction to be interruptible and reversible • Streamline interaction as skill level increases and allow customization of interaction • Hide technical internals from the casual user • Design for direct interaction with objects that appear on the screen

5. Reduce Memory Load • Reduce demands on user's short-term memory • Establish meaningful defaults • Define intuitive short-cuts • Visual layout of user interface should be based on a familiar real world metaphor • Disclose information in a progressive fashion

6. Make Interface Consistent • Allow user to put the current task into a meaningful context • Maintain consistency across a family of applications • If past interaction models have created user expectations, do not make changes unless there is a good reason to do so

7. User Interface Design Models • Design model • incorporates data, architectural, interface, and procedural representations of the software • User model (end user profiles) • novice, • knowledgeable intermittent user • knowledgeable frequent users • User's model or system perception • user's mental image of system • System image • look and feel of the interface and supporting media

8. User Interface Design Process(spiral model) • User, task, and environment analysis and modeling • Interface design • Interface construction • Interface validation

9. Task Analysis and Modeling - 1 • Software engineer • studies tasks human users must complete to accomplish their goals without the computer • maps these into a similar set of tasks that are to be implemented in the user interface • Software engineer • studies existing specification for computer solution • derives a set of tasks that will accommodate the user model, design model, and system perception

10. Task Analysis and Modeling - 2 • Software engineer • may devise an object-oriented approach by observing the real world objects and user actions (use cases) • models the interface objects after their real world counterparts

11. Interface Design Activities • Establish goals and intentions for each task • Map each goal/intention to a sequence of actions (methods for manipulating objects) • Specify the action sequence of tasks and subtasks (user scenario) • Indicate the state of the system at the time the user scenario is performed • Define control mechanisms • Show how control mechanisms affect the state of the system • Indicate how the user interprets state of the system from information provided through the interface

12. Interface Design Issues • System response time • time between the point at which user initiates some action and the time the system responds • User help facilities • integrated, context sensitive help • add-on help • Error information handling • messages should be non-judgmental • describe problem precisely • suggest valid solutions

13. Data Display Guidelines • Consistency • Efficient information assimilation by user • Minimal memory load on user • Compatibility between data display and data entry • Flexibility of user control over data display

14. Data Entry Guidelines • Consistency • Minimal user input actions • Minimal memory load on user • Compatibility between data entry and data display • Flexible user control

15. Getting User’s Attention • Intensity (2 levels only) • Marking (e.g. underscore) • Fonts (up to 3) • Inverse video • Blinking (2 to 4 hertz) • Color (up to 4 standard colors) • Color blinking • Audio

16. Factors affecting choice of evaluation methodology • Stage of design • Novelty of product • Expected number of users • Criticality of interface • Cost of product and budget for testing • Experience of design and evaluation teams

17. User Interface Evaluation • Preliminary design • Build first interface prototype • User evaluates interface • Evaluation results studied by designer • Design modifications made • Build next prototype • If interface is not complete then go to step 3

18. User Interface Evaluation Criteria - 1 • Length and complexity of written interface specification • indicate of amount of learning required by system users • Number of user tasks and the average number of actions per task • indicate of interaction time and overall system efficiency

19. User Interface Evaluation Criteria - 2 • Number of tasks, actions, and system states in the design model • indicate of the memory load required of system users • Interface style, help facilities, and error handling protocols • indicate of system complexity and likely degree of acceptance by the users