Designing the User Interface Theories, Principles, and Guidelines Course 4, CMC, 23/09/03

23/09/03HC42 Designing User Interfaces “Designing user interfaces is a complex and highly creative process that blends intuition, experience, and careful consideration of numerous technical issues” Ben Shneiderman (1998, 3rd ed.)

23/09/03HC43 User Interface Locus of interaction Cushioning buffer Visible aspect of the invisible system

23/09/03HC44 Human-Machine Loop Perceptual system detects state Display tells user machine’s state Controls allow user to affect machine’s state Effector system operates controls

23/09/03HC45 Goals of Interactive Systems Simplifying user’s tasks –routine tasks –tedious tasks –error-prone tasks Eliminating human actions when no judgment is required

23/09/03HC46 Causes user’s frustration, fear and failure Excessive complexity Incomprehensible terminology Chaotic layouts

23/09/03HC47 High-quality interactive systems I Beyond vague notion of “user friendliness” Thoughtful planning Sensitivity to user needs Diligent testing

23/09/03HC48 High-quality interactive systems II Positive feelings of success, competence, mastery, clarity Interface almost disappears Interface is comprehensible and predictable Interface masks underlying computational complexity Users remain “in the flow”

23/09/03HC49 Goals of system engineering Adequate functionality (task analysis) Reliability Standardization Schedule and budgetary planning

23/09/03HC410 Goals of Interface Design Design and testing of multiple alternatives –for specific user communities –for specific tasks Measurable human factors –time to learn –speed of performance –rate of errors –retention over time –subjective satisfaction

23/09/03HC411 Guidance for designers High-level theories and models Middle-level principles Specific and practical guidelines

23/09/03HC412 High-level theories I Four-level approach of Foley & van Dam (1990): conceptual-semantic- syntactic-lexical GOMS and the keystroke-level model Card, Moran& Newell (1980,1983); Kieras & Polson (1985); Kieras (1988); Elkerton & Palmiter (1991)

23/09/03HC413 High-level theories II Stages-of-actions models: Norman (1988)’s 7 stages of action –forming goal –forming intention –specifying action –executing action –perceiving system state –interpreting system state –evaluating outcome

23/09/03HC414 High-level theories III Consistency through action grammars: Reisner (1981); Payne & Green (1986) –task[Direction, Unit] -> symbol[Direction] + letter[Unit] –symbol[Direction=forward] -> “CTRL” –symbol[Direction=backward] -> “ESC” –letter[Unit=word] -> “W” –letter[Unit=character] -> “C”

23/09/03HC415 High-level theories IV Widget-level theories: Object-Action Interface Model of Shneiderman (1980, 1981, 1983) –Hierarchies of task objects and actions –Hierarchies of interface objects and actions –Metaphoric representation conveys interface objects and actions – Tuning of interface objects and actions to fit the task –Direct manipulation approach to design –Minimizing burdens of syntax

23/09/03HC416 Middle-level Principles Principle 1: recognize diversity Principle 2: use the 8 golden rules of interface design Principle 3: prevent errors

23/09/03HC417 Recognize diversity I Usage profiles –novice or first-time users –knowledgeable intermittent users –expert frequent users Accommodation of one system to different usage classes –level-structured learning –user control of density of informative feedback

23/09/03HC418 Recognize diversity II Task Profiles –appropriate sets of atomic objects and actions –relative task frequencies Primary Interaction Styles –direct manipulation –menu selection –form fillin –command language –natural language

23/09/03HC419 8 Golden Rules of Interface Design Strive for consistency Enable frequent users to use shortcuts Offer 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

23/09/03HC420 Prevent Errors Correct matching pairs Complete sequences of actions Correct commands Direct manipulation strategies

23/09/03HC421 Summary Task analysis “Know thy user” Recording task objects and actions Construction of suitable interface objects and actions Extensive testing Iterative refinement

23/09/03HC422 Points to discuss Faulkner, Raskin, Sutcliffe Oulanov & Pajarillo Usability Evaluation of OPC Contribution of Communication and Information Science to HCI