Principles and Methods User Interface Design 1 Principles and Methods

User interface metaphors dialogue metaphor direct manipulation (event-driven, GUI) metaphor

User Interface Design Guidelines Consistency – helps a user learn an application and apply what they know across different parts of that application. Guidelines in corporate style guides help here (e.g. Microsoft UX).

User Interface Design Guidelines 2. Appropriate User Support- when the user does not know what action to take or has made an error.

User Interface Design Guidelines 3. Adequate Feedback Show the user what is happening e.g. cursor position, eggtimer, progress monitor, status bar, highlighting, boxing.

User Interface Design Guidelines 4. Minimal User Input use of codes and abbreviations selecting from a list rather than typing in a value not having to enter information that can be derived automatically, using default values. Key combinations can be used to speed things up for expert users.

Style Guides Microsoft Windows Application user interface development guidelines http://msdn.microsoft.com/en-us/library/ff657751(v=VS.85).aspx Windows UX- User Experience Interaction Guidelines http://msdn.microsoft.com/en-us/library/aa511258.aspx

Visual Index http://msdn.microsoft.com/en-us/library/bb328626.aspx This shows guidelines for the use of wpf components – when and how to use them, common mis-uses.

Approaches to design Structured – uses task hierarchies e.g. STUDIO: task hierarchy diagrams, knowledge representation grammars, task allocation charts, state machines. Ethnographic – detailed qualitative study of users and tasks Scenario-based - draw out storyboards of scenarios , or describe them textually. Aspects of all approaches can be combined.

1. Structured UI Design: Stages Requirements gathering determine the types of user, frequency of use, task experience level, computing skills etc. Determine task characteristics : complexity, breakdown, goal, context, task environment Constraints, objectives, hardware, software, desired throughput, acceptable error rate Interface design – allocate elements of task to user/system, determine communication requirements, design interface elements to support communication. Interface evaluation – develop prototypes and test on users.

Task Hierarchy Breakdown * Sequence Repetition (iteration) o o Selection

Example Book Flight Enter Flight details Show Flights available Take Payment Confirm Booking Existing customer O New Customer O Show flights and prices * Select flight O Abandon O

State Machines - similar to UML – more on this later

Ethnographic Approaches Qualitative assessment of task situation where the designer works very closely with the user in their work context. Observing Listening Asking questions Interviews E.g. Participative design

Scenario-based Approaches Step-by step descriptions of user actions showing how users can achieve a goal Can use textual narrative or storyboards.

Usability Criteria Learnability - time and effort needed Throughput of the expert user Flexibility – ability to handle changes to tasks and the environment in which they operate. Attitude – how positive does the user feel as a result of his/her experience with the package?   ISO definition of Usability : degree to which users can achieve specific goals in a particular environment ; effectively, efficiently, comfortably and in an acceptable manner

Standards and Legal Requirements Accessibility standards Web accessibility initiative ISO usability standards http://www.usabilitynet.org/tools/r_international.htm http://www.w3.org/WAI/intro/wai-age-literature.php

Schneidermans Golden Rules Strive for consistency. Consistent sequences of actions should be required in similar situations; identical terminology should be used in prompts, menus, and help screens; and consistent commands should be employed throughout. Enable frequent users to use shortcuts. Offer informative feedback.

Schneidermans Golden Rules Design dialog to yield closure. Sequences of actions should be organized into groups with a beginning, middle, and end. The informative feedback at the completion of a group of actions gives the operators the satisfaction of accomplishment, a sense of relief, the signal to drop contingency plans and options from their minds, and an indication that the way is clear to prepare for the next group of actions. Offer simple error handling. As much as possible, design the system so the user cannot make a serious error. If an error is made, the system should be able to detect the error and offer simple, comprehensible mechanisms for handling the error. Permit easy reversal of actions. Support internal locus of control. Design the system to make users the initiators of actions rather than the responders. Minimise memorisation Adapted from from http://www.cs.utexas.edu/users/almstrum/cs370/elvisino/rules.html