User Interface Design & Implementation. Prof. Dr.-Ing. Abdulmotaleb El Saddik University of Ottawa (SITE 5-037) (613) x 6277

Transcription

1 SEG 3210 User Interface Design & Implementation Prof. Dr.-Ing. Abdulmotaleb El Saddik University of Ottawa (SITE 5-037) (613) x 6277 site.uottawa.ca mcrlab.uottawa.ca

2 Unit A: Introduction to HCI 1. Why study user interface design? 2. History 3. Goals of HCI 4. Five key ideas in HCI 5. Optical Illusions 6. Understanding users 7. User productivity and usability 8. Disciplines contributing to HCI 9. HCI engineering as a branch of software engineering 10. User interface malfunctions 11. Case studies in user interface malfunction 12. Key points to review

3 Definition The study of people and computing and the way they influence each other A set of processes, dialogues, and actions through which a human user employs and interacts with a computer A discipline concerned with the design, evaluation and implementation of interactive computing systems for human use with the study of major phenomena surrounding them

4 1. Why Study User Interface Design? 75% or more of development effort can go into the user interface 40% to 70% is typical User interface specialists are needed Everybody needs to know the basics User interface software is becoming more complex Complexity increase is faster than other aspects of systems Graphical user interfaces have provided the biggest jump in complexity Applications tend to grow to fill available computing resources There are direct financial benefits from improved user interfaces

5 Financial benefits & Costs of improved user interfaces Increased user productivity Direct financial savings Increased revenues from sales The system is more attractive and customer satisfaction is higher Decreased training and support costs The system is more intuitive Decreased maintenance cost The system does what user wants Much maintenance involves fixing UI problems Pay a little during development, or pay a lot after application/product release! But Staff must be trained in user interface analysis and design Users must participate UI design tools are needed. The benefits almost always outweigh the costs

6 2. History Early days of computing: Computers cost more than people Computers had little functionality The UI was unimportant Early 1970s Field of Man Machine Interface (MMI) born. Term changed gradually to User Interface (UI) Ideas for first Graphical User Interface (GUI) Dynabook at Xerox Late 1970s and 1980s Products were called user friendly No science in this: Just a market buzzword First real GUI s developed Xerox Star --> Smalltalk and Macintosh

7 2. History (Cont d) 1980s Term Human-Computer Interaction (HCI or CHI) came into use wider scope than UI (help, work practices etc.) MS-Windows, X-Windows follow the Mac Intense research into HCI 1990s and early 2000s Virtual reality, speech and handwriting I/O, Soundblaster Good BUT also Bad UI s continue to be developed!!!

8 3. Goals of HCI Improve productivity and reduce costs through: Safety: Does the system prevent danger? Functionality: How many things can the system do? Efficiency: How few resources does it take to get a task done? Usability : How easy to learn and use is the system? BUT High functionality (many ways of doing the same thing) can actually reduce usability By causing confusion

9 4. Five Key Ideas in HCI Visibility The UI should help the user always understand... The current state of the system What operations can be done E.g. When you position the cursor over a point on the screen, it should be clear what would happen if you clicked the mouse Many design guidelines in unit E will help improve visibility Feedback When anything changes it should be made visible When you delete a file, the system should not just say ready Goal A state the user wants to reach to be talking with somebody on the phone to have saved a file

10 4. Five Key Ideas in HCI (Cont d) Affordance The set of operations and procedures that can be done to an object Perceived affordance is what typical users think can be done to an object Should a door be pulled or pushed? What does this icon mean? To improve visibility/feedback we need to: Choose objects with good perceived affordance Design the UI to generate better perceived affordance Task An action the user wants to do to call somebody to save the file Goals beget tasks, tasks beget goals. Unit C focuses on task analysis and gives good conceptual models which will help us achieve this

11 5. Optical Illusions

12 5. Optical Illusions (Cont d) The quick brown fox jumps over the the lazy dog.

13 5. Optical Illusions (Cont d) Now read through the following sentence counting aloud the "F"s as you find them ( etc). Count them ONLY ONCE: Do not go back and count them again!!!. OK - GO! FINISHED FILES ARE THE RESULT OF YEARS OF SCIENTIFIC STUDY COMBINED WITH THE EXPERIENCE OF YEARS.

14 6. Understanding Users Dual Processor" Theory: Every interactive system is a distributed system running on two processors: Human User user interface Computer System User interface design specifies/constrains both: User behaviour System behaviour We must understand the nature of the human processors Each kind should be considered when designing the UI

15 6. Understanding Users (Cont d) Users can be categorized: By class Determined by the pattern of use: e.g., manager, salesperson, shipper, client By personality type Shy or reticent Inarticulate Disinterested or defensive Intimidated Involved designer! By ability Physical disability --> innovative I/O may be needed Colourblind --> don t use colours as the only means of conveying information Dyslexia or other cognitive glitches --> watch out for left vs. right! Illiteracy --> icons may be needed Computer illiteracy Ignorance of domain / learner

16 7. User Productivity & Usability User productivity = Functionality (what the computer can do) * Usability (what people can do with the computer) If either of these is zero, the system is useless Factors Influencing User Productivity Kind and number of tasks Characteristics of users (ability, experience etc.) Work environment (distractions etc.) Training and documentation Functionality and usability of available software and hardware

17 A Model of Usability Factors enjoyability satisfaction acceptability usability primary functionality ergonomics efficiency of use learnability extensibility/customization ease of use familiarity error handling fit to task cognitive load fit to user

18 Critical Usability Factors High staff turnover Discretionary use Learnability critical Fit to task critical Prolonged or frequent use Efficiency critical Creative use High functionality Ease of extension and customization critical Higher usability needed Infrequent discretionary use of highly functional system with staff turnover A problem!

19 8. Disciplines Contributing to HCI Cognitive psychology Capabilities and limitations of human senses and thought processes Ergonomics Hardware and software efficiency of use and safety Linguistics Syntax and semantics of commands Speech I/O Artificial intelligence Speech I/O Intelligent guessing what the user wants to do Knowledge representations of users and tasks Sociology and social psychology Assisting people to work in groups with software Ensuring software works in different cultures Engineering and industrial design Disciplined measurement-based approaches Esthetics Storyboarding etc.

20 Human Cognitive system Perception and representation Some displays can be hard to interpret Blue foreground Optical illusions Contrast in colour but not brightness Too many colours There are two ways to use graphics: For modeling direct images of concepts For coding representing underlying ideas, e.g., displaying quantitative data

21 Human Cognitive system (Cont d) Attention limitations People can be readily distracted Provide cues about what to focus on People get lost in complexity Structure information so it is easy to browse through not too many items not too few items grouped logically People multitask Make the state clear so users can jump backwards and forwards Some mental processes are automatic, or become so (contrasted with controlled processes) These processes are very hard to unlearn

22 Human Cognitive system (Cont d) Memory limitations Short term memory can contain 7±2 chunks Avoid situations where users have to remember more than this Logically group things so users can chunk them The more meaningful, the more easily remembered (familiarity, imagery and consistency contribute to meaningfulness) Use effective names and icons (even) animated ones Combine icons with words Icons can be analogies, examples or abstract, but not arbitrary Watch out for cultural differences (e.g. washroom symbols) People can more easily recognize than recall Use menus, icons, quick lookup

23 9. HCI Eng. as a Branch of SW Eng. (Unit C&D) A conceptual model of the user interface development process: Star model Evaluation is the central process UI is repeatedly revised when problems are found Implementation Task analysis/ functional analysis Detailed design Evaluation Requirements specification Prototyping Conceptual design

24 A five level conceptual model of the UI At each level: Design must be done Problems can occur 1. Task Level What is to be done by the user 2. Conceptual Level User s intended mental model of the system 3. Interaction Style Level Command-driven, menu-driven, direct manipulation, hypermedia Design elements that are repeated throughout the system 4. Interaction Element Level Specific windows, dialogs, commands, menus 5. Physical Element Level Bitmaps, characters, data structures, callbacks

25 Evolution from plain SW- to usability Eng. Normal software development (involving the UI) Focuses on physical and interaction elements Waterfall model dominates (sequential), Spiral model Evaluation by functional spec reviews and testing User interface development Focuses on users and tasks Star model dominates (iterative) Evaluation by continuous user involvement Driven by heuristics and guidelines Integrates psychology etc. Influence on functionality Usability engineering Driven by engineering objectives Integrates rigorous engineering discipline Drives functionality

26 A conceptual model of user interface system architecture User interface layer API (low-level commands) Functional layer(s) (focus of task analysis and conceptual modelling) (focus of functional analysis) Why layers? Simplifies software development and maintenance Both layers: Are developed in parallel Influence each other Included in complete system specifications Evaluated together Evolution of layers: Functional layer should need to change less often during iterative tuning of the interface Both layers may need to change when business functions change but hopefully interaction styles should remain similar

27 Characteristics of Products and Applications Each kind of application puts different demands on the UI designer Application for internal use vs. product for sale Generic utility vs. task-specific tool Walk-up-and-use vs. skilled usage Some design challenges: Customizing a generic utility product so that it becomes a taskspecific tool for internal use and vice versa Converting an application requiring skilled usage to make it a walkup-and-use application

28 10. User Interface Malfunctions Key idea: There are no good user interfaces... just user interfaces that fit A truly bad user interface never fits But among the good ones, some will suit one task/user; some with suit another To maximize fitness, we must minimize the occurrence of malfunctions in the context of the expected use of the system

29 Definitions of malfunction A mismatch between what the user wants, needs or expects and what the system provides A breakdown in usability An obstacle to performing a desired task You should know that: Occasional malfunctions are normal Systematic or frequent malfunctions need to be fixed

30 Related ideas to malfunction Error: Identifiable mistake on the part of the designer Defect: A deviation from what the user needs A malfunction is a usability defect A defect in the smooth functioning of the user/computer system! Users may not be aware of many malfunctions the malfunctions may only be located through careful analysis they may be subtle More discussion of malfunctions in unit B

31 11. Case Studies in UI malfunctions Aircraft disasters China Airlines pilot loses control: Human was expected to act as a monitor, but humans are bad monitors (get bored) Humans need to control things and get feedback US Vincennes downs Iranian jet; 290 lives lost Critical information about the plane was on different displays When gathering relevant facts from different places, a wrong match was made

32 12. Key Points to Review Goals of HCI: Improve safety functionality efficiency usability Visibility and feedback Affordance and perceived affordance Goal = state; task = action Human/computer as system running on 2 processors Types, classes and abilities of users Productivity = functionality * usability Usability factors e.g. learnability, fit, acceptability Contributing disciplines e.g. linguistics, Artificial Intelligence

33 12. Key Points to Review Human cognitive system - Limitations on: perception attention memory Task analysis vs. functional analysis Star model with evaluation at centre UI levels task conceptual model interaction style interaction element physical element Usability engineering Layered approach with an API Malfunction as a kind of defect (of usability)