Nota sendiri hci-HCI


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Nota sendiri hci-HCI

  1. 1. Donald Norman‟s model Seven stages ◦ user establishes the goal ◦ formulates intention ◦ specifies actions at interface ◦ executes action ◦ perceives system state ◦ interprets system state ◦ evaluates system state with respect to goal Norman‟s model concentrates on user‟s view of the interface shafyHCI/sem5_KSS
  2. 2. execution/evaluation loop goal execution evaluation system  user establishes the goal  formulates intention  specifies actions at interface  executes action  perceives system state  interprets system state  evaluates system state with respect to goal shafyHCI/sem5_KSS
  3. 3. Ergonomics Study of the physical characteristics of interaction Also known as human factors – but this can also be used to mean much of HCI! Ergonomics good at defining standards and guidelines for constraining the way we design certain aspects of systems shafyHCI/sem5_KSS
  4. 4. Ergonomics - examples arrangement of controls and displays e.g. controls grouped according to function or frequency of use, or sequentially surrounding environment e.g. seating arrangements adaptable to cope with all sizes of user health issues e.g. physical position, environmental conditions (temperature, humidity), lighting, noise, use of colour e.g. use of red for warning, green for okay, awareness of colour-blindness etc. shafyHCI/sem5_KSS
  5. 5. Common interaction styles command line interface menus natural language question/answer and query dialogue form-fills and spreadsheets WIMP point and click three–dimensional interfaces shafyHCI/sem5_KSS
  6. 6. Command line interface Way of expressing instructions to the computer directly ◦ function keys, single characters, short abbreviations, whole words, or a combination suitable for repetitive tasks better for expert users than novices offers direct access to system functionality command names/abbreviations should be meaningful!Typical example: the Unix system shafyHCI/sem5_KSS
  7. 7. Menus Set of options displayed on the screen Options visible ◦ less recall - easier to use ◦ rely on recognition so names should be meaningful Selection by: ◦ numbers, letters, arrow keys, mouse ◦ combination (e.g. mouse plus accelerators) Often options hierarchically grouped ◦ sensible grouping is needed Restricted form of full WIMP system shafyHCI/sem5_KSS
  8. 8. Natural language Familiar to user speech recognition or typed natural language Problems ◦ vague ◦ ambiguous ◦ hard to do well! Solutions ◦ try to understand a subset ◦ pick on key words shafyHCI/sem5_KSS
  9. 9. Query interfaces Question/answer interfaces ◦ user led through interaction via series of questions ◦ suitable for novice users but restricted functionality ◦ often used in information systems Query languages (e.g. SQL) ◦ used to retrieve information from database ◦ requires understanding of database structure and language syntax, hence requires some expertise shafyHCI/sem5_KSS
  10. 10. Form-fills Primarily for data entry or data retrieval Screen like paper form. Data put in relevant place Requires ◦ good design ◦ obvious correction facilities shafyHCI/sem5_KSS
  11. 11. Spreadsheets first spreadsheet VISICALC, followed by Lotus 1-2-3 MS Excel most common today sophisticated variation of form-filling. ◦ grid of cells contain a value or a formula ◦ formula can involve values of other cells e.g. sum of all cells in this column ◦ user can enter and alter data spreadsheet maintains consistency shafyHCI/sem5_KSS
  12. 12. WIMP Interface Windows Icons Menus Pointers … or windows, icons, mice, and pull-down menus! default style for majority of interactive computer systems, especially PCs and desktop machines shafyHCI/sem5_KSS
  13. 13. Physical design many constraints: ◦ ergonomic – minimum button size ◦ physical – high-voltage switches are big ◦ legal and safety – high cooker controls ◦ context and environment – easy to clean ◦ aesthetic – must look good ◦ economic – … and not cost too much! shafyHCI/sem5_KSS
  14. 14. Personal computing 1970s – Paperts LOGO language for simple graphics programming by children A system is more powerful as it becomes easier to user Future of computing in small, powerful machines dedicated to the individual Kay at Xerox PARC – the Dynabook as the ultimate personal computer shafyHCI/sem5_KSS
  15. 15. Window systems and the WIMPinterface humans can pursue more than one task at a time windows used for dialogue partitioning, to “change the topic” 1981 – Xerox Star first commercial windowing system windows, icons, menus and pointers now familiar interaction mechanisms shafyHCI/sem5_KSS
  16. 16. Metaphor relating computing to other real-world activity is effective teaching technique ◦ LOGOs turtle dragging its tail ◦ file management on an office desktop ◦ word processing as typing ◦ financial analysis on spreadsheets ◦ virtual reality – user inside the metaphor Problems ◦ some tasks do not fit into a given metaphor ◦ cultural bias shafyHCI/sem5_KSS
  17. 17. the software lifecycle Software engineering is the discipline for understanding the software design process, or life cycle Designing for usability occurs at all stages of the life cycle, not as a single isolated activity shafyHCI/sem5_KSS
  18. 18. The waterfall model Requirements specification Architectural design Detailed design Coding and unit testing Integration and testing Operation and maintenance shafyHCI/sem5_KSS
  19. 19. Activities in the life cycleRequirements specification designer and customer try capture what the system is expected to provide can be expressed in natural language or more precise languages, such as a task analysis would provideArchitectural design high-level description of how the system will provide the services required factor system into major components of the system and how they are interrelated needs to satisfy both functional and nonfunctional requirementsDetailed design refinement of architectural components and interrelations to identify modules to be implemented separately the refinement is governed by the nonfunctional requirements shafyHCI/sem5_KSS
  20. 20. Verification and validation Real-world requirements and constraints The formality gapVerification designing the product rightValidation designing the right productThe formality gap validation will always rely to some extent on subjective means of proofManagement and contractual issues design in commercial and legal contexts shafyHCI/sem5_KSS
  21. 21. The life cycle for interactivesystems cannot assume a linear sequence of activitiesRequirementsspecification as in the waterfall model Architectural design Detailed design Coding and unit testinglots of feedback! Integration and testing Operation and maintenance shafyHCI/sem5_KSS
  22. 22. Usability engineeringThe ultimate test of usability based on measurement of user experienceUsability engineering demands that specific usability measures be made explicit as requirementsUsability specification ◦ usability attribute/principle ◦ measuring concept ◦ measuring method ◦ now level/ worst case/ planned level/ best caseProblems ◦ usability specification requires level of detail that may not be ◦ possible early in design satisfying a usability specification ◦ does not necessarily satisfy usability shafyHCI/sem5_KSS
  23. 23. ISO usability standard 9241adopts traditional usability categories: effectiveness ◦ can you achieve what you want to? efficiency ◦ can you do it without wasting effort? satisfaction ◦ do you enjoy the process? shafyHCI/sem5_KSS
  24. 24. Iterative design andprototyping Iterative design overcomes inherent problems of incomplete requirements Prototypes ◦ simulate or animate some features of intended system ◦ different types of prototypes  throw-away  incremental  evolutionary Management issues ◦ time ◦ planning ◦ non-functional features ◦ contracts shafyHCI/sem5_KSS
  25. 25. Techniques for prototypingStoryboards need not be computer-based can be animatedLimited functionality simulations some part of system functionality provided by designers tools like HyperCard are common for these Wizard of Oz techniqueWarning about iterative design design inertia – early bad decisions stay bad diagnosing real usability problems in prototypes…. …. and not just the symptoms shafyHCI/sem5_KSS
  26. 26. Design rationaleDesign rationale is information that explains why acomputer system is the way it is.Benefits of design rationale ◦ communication throughout life cycle ◦ reuse of design knowledge across products ◦ enforces design discipline ◦ presents arguments for design trade-offs ◦ organizes potentially large design space ◦ capturing contextual information shafyHCI/sem5_KSS
  27. 27. Design rationale (cont‟d)Types of DR: Process-oriented ◦ preserves order of deliberation and decision-making Structure-oriented ◦ emphasizes post hoc structuring of considered design alternatives Two examples: ◦ Issue-based information system (IBIS) ◦ Design space analysis shafyHCI/sem5_KSS
  28. 28. Issue-based information system(IBIS) basis for much of design rationale research process-oriented main elements: issues – hierarchical structure with one „root‟ issue positions – potential resolutions of an issue arguments – modify the relationship between positions and issues gIBIS is a graphical version shafyHCI/sem5_KSS
  29. 29. structure of gIBIS supports Position Argument responds to Issue responds to objects to Position Argument specializesSub-issue generalizes questions Sub-issue Sub-issue shafyHCI/sem5_KSS
  30. 30. Design space analysis structure-oriented QOC – hierarchical structure: questions (and sub-questions) – represent major issues of a design options – provide alternative solutions to the question criteria – the means to assess the options in order to make a choice DRL – similar to QOC with a larger language and more formal semantics shafyHCI/sem5_KSS
  31. 31. the QOC notation Criterion OptionQuestion Option Criterion Option Criterion … Consequent …Question Question shafyHCI/sem5_KSS
  32. 32. Psychological designrationale to support task-artefact cycle in which user tasks are affected by the systems they use aims to make explicit consequences of design for users designers identify tasks system will support scenarios are suggested to test task users are observed on system psychological claims of system made explicit negative aspects of design can be used to improve next iteration of design shafyHCI/sem5_KSS
  33. 33. SummaryThe software engineering life cycle ◦ distinct activities and the consequences for interactive system designUsability engineering ◦ making usability measurements explicit as requirementsIterative design and prototyping ◦ limited functionality simulations and animationsDesign rationale ◦ recording design knowledge ◦ process vs. structure shafyHCI/sem5_KSS
  34. 34. chapter 2design rules shafyHCI/sem5_KSS
  35. 35. design rulesDesigning for maximum usability – the goal of interaction design Principles of usability ◦ general understanding Standards and guidelines ◦ direction for design Design patterns ◦ capture and reuse design knowledge shafyHCI/sem5_KSS
  36. 36. types of design rules principles ◦ abstract design rules ◦ low authority ◦ high generality standards Guide line s increasing generality ◦ specific design rules inc reasin g gen eralit y ◦ high authority ◦ limited application guidelines Standar ds ◦ lower authority ◦ more general application increasing auth ority increasing authority shafyHCI/sem5_KSS
  37. 37. Principles to support usabilityLearnability the ease with which new users can begin effective interaction and achieve maximal performanceFlexibility the multiplicity of ways the user and system exchange informationRobustness the level of support provided the user in determining successful achievement and assessment of goal-directed behaviour shafyHCI/sem5_KSS
  38. 38. Principles of learnabilityPredictability ◦ determining effect of future actions based on past interaction history ◦ operation visibilitySynthesizability ◦ assessing the effect of past actions ◦ immediate vs. eventual honesty shafyHCI/sem5_KSS
  39. 39. Principles of learnability (ctd)Familiarity ◦ how prior knowledge applies to new system ◦ guessability; affordanceGeneralizability ◦ extending specific interaction knowledge to new situationsConsistency ◦ likeness in input/output behaviour arising from similar situations or task objectives shafyHCI/sem5_KSS
  40. 40. Principles of flexibilityDialogue initiative ◦ freedom from system imposed constraints on input dialogue ◦ system vs. user pre-emptivenessMultithreading ◦ ability of system to support user interaction for more than one task at a time ◦ concurrent vs. interleaving; multimodalityTask migratability ◦ passing responsibility for task execution between user and system shafyHCI/sem5_KSS
  41. 41. Principles of flexibility (ctd)Substitutivity ◦ allowing equivalent values of input and output to be substituted for each other ◦ representation multiplicity; equal opportunityCustomizability ◦ modifiability of the user interface by user (adaptability) or system (adaptivity) shafyHCI/sem5_KSS
  42. 42. Principles of robustnessObservability ◦ ability of user to evaluate the internal state of the system from its perceivable representation ◦ browsability; defaults; reachability; persistence; operation visibilityRecoverability ◦ ability of user to take corrective action once an error has been recognized ◦ reachability; forward/backward recovery; commensurate effort shafyHCI/sem5_KSS
  43. 43. Principles of robustness (ctd)Responsiveness ◦ how the user perceives the rate of communication with the system ◦ StabilityTask conformance ◦ degree to which system services support all of the users tasks ◦ task completeness; task adequacy shafyHCI/sem5_KSS
  44. 44. Using design rules increasing generality Guide line s inc reas in g gen eralit yDesign rules suggest how to increase usability differ in generality and authority Standar ds increasing auth ority increasing authority shafyHCI/sem5_KSS
  45. 45. Standards set by national or international bodies to ensure compliance by a large community of designers standards require sound underlying theory and slowly changing technology hardware standards more common than software high authority and low level of detail ISO 9241 defines usability as effectiveness, efficiency and satisfaction with which users accomplish tasks shafyHCI/sem5_KSS
  46. 46. Guidelines more suggestive and general many textbooks and reports full of guidelines abstract guidelines (principles) applicable during early life cycle activities detailed guidelines (style guides) applicable during later life cycle activities understanding justification for guidelines aids in resolving conflicts shafyHCI/sem5_KSS
  47. 47. Golden rules and heuristics “Broad brush” design rules Useful check list for good design Better design using these than using nothing! Different collections e.g. ◦ Nielsen‟s 10 Heuristics (see Chapter 9) ◦ Shneiderman‟s 8 Golden Rules ◦ Norman‟s 7 Principles shafyHCI/sem5_KSS
  48. 48. Shneiderman‟s 8 GoldenRules1. Strive for consistency2. Enable frequent users to use shortcuts3. Offer informative feedback4. Design dialogs to yield closure5. Offer error prevention and simple error handling6. Permit easy reversal of actions7. Support internal locus of control8. Reduce short-term memory load shafyHCI/sem5_KSS
  49. 49. Norman‟s 7 Principles1. Use both knowledge in the world and knowledge in the head.2. Simplify the structure of tasks.3. Make things visible: bridge the gulfs of Execution and Evaluation.4. Get the mappings right.5. Exploit the power of constraints, both natural and artificial.6. Design for error.7. When all else fails, standardize. shafyHCI/sem5_KSS
  50. 50. HCI design patterns An approach to reusing knowledge about successful design solutions Originated in architecture: Alexander A pattern is an invariant solution to a recurrent problem within a specific context. Examples ◦ Light on Two Sides of Every Room (architecture) ◦ Go back to a safe place (HCI) Patterns do not exist in isolation but are linked to other patterns in languages which enable complete designs to be generated shafyHCI/sem5_KSS
  51. 51. HCI design patterns (cont.) Characteristics of patterns ◦ capture design practice not theory ◦ capture the essential common properties of good examples of design ◦ represent design knowledge at varying levels: social, organisational, conceptual, detailed ◦ embody values and can express what is humane in interface design ◦ are intuitive and readable and can therefore be used for communication between all stakeholders ◦ a pattern language should be generative and assist in the development of complete designs. shafyHCI/sem5_KSS
  52. 52. SummaryPrinciples for usability ◦ repeatable design for usability relies on maximizing benefit of one good design by abstracting out the general properties which can direct purposeful design ◦ The success of designing for usability requires both creative insight (new paradigms) and purposeful principled practiceUsing design rules ◦ standards and guidelines to direct design activity shafyHCI/sem5_KSS