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CMC/CC A Task Analysis

CMC/CC A Task Analysis. Master IK, CIW, MMI L.M. Bosveld-de Smet Hoorcollege 4; ma. 25 sept. 2006; 16.00-18.00. Goals of system engineering. Adequate functionality What tasks and subtasks must be carried out? Task analysis is central! Reliability Standardization

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CMC/CC A Task Analysis

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  1. CMC/CC ATask Analysis Master IK, CIW, MMI L.M. Bosveld-de Smet Hoorcollege 4; ma. 25 sept. 2006; 16.00-18.00

  2. Goals of system engineering • Adequate functionality • What tasks and subtasks must be carried out? • Task analysis is central! • Reliability • Standardization • Schedule and budgetary planning • Attention to human factors • Rigorous testing

  3. Process of design in HCI • Requirements • what is wanted? • Analysis • Task models – means to capture how people carry out tasks • Design • Modeling and describing interaction • Theories, design principles (basic heuristics), guidelines • Iteration and prototyping • Implementation and deployment

  4. Task Analysis • Process of analyzing the way people perform their jobs • Essential part of Requirements Analysis • Essential part of HCI Design • Failure may result in serious usability problems

  5. Task Analysis: different approaches • Task decomposition • Looks at the way a task is split into subtasks, and the order in which these are performed • Knowledge-based techniques • Look at what users need to know about the objects and actions involved in a task, and how that knowledge is organized • Entity-relation-based analysis • Object-based approach, where emphasis is on identifying actors and objects, the relationships between them and the actions they perform

  6. Task Decomposition: HTA example 0. In order to clean a house 1. get the vacuum cleaner out 2. fix the appropriate attachment 3. clean the rooms 3.1. clean the hall 3.2. clean the living rooms 3.3. clean the bedrooms 4. empty the dust bag 5. put the vacuum cleaner and attachments away Plan 0: do 1-2-3-5 in that order; when the dust bag gets full do 4. Plan 3: do 3.1 every day; do 3.2 once a week; when visitors are due do 3.3

  7. HTA: making a cup of tea Plan 0 Do1; at the same time, if the pot is full do2; Then do 3-4; After 4 or 5 minutes do 6 0. make a cup of tea 1. Boil water 2. Empty pot 3. Put tea leaves In pot 4. Pour in boiling water 5. Wait 4 or 5 minutes 6. Pour tea 1.1. Fill kettle 1.2. Put kettle on hob 1.3. Wait for kettle to boil 1.4. Turn off gas Plan 1 Do 1.1-1.2-1.3 When kettle boils do 1.4

  8. HTA for making lots of cups of tea Plan 0 Do1; at the same time, if the pot is full do2; Then do 3-4; After 4 or 5 minutes do 5 Plan 1 Do 1.1-1.2-1.3-1.4 When kettle boils do 1.5 0. make cups of tea 1. Boil water 2. Empty pot 3. Make pot 4. Wait 4 or 5 minutes 5. Pour tea 5.1. Put milk in cup 5.2. Fill cup with tea 5.3. Do sugar Plan 3 3.1-3.2-3.3 3.1. Warm pot 3.2. Put tea leaves in pot 3.3. Pour in boiling water 5.3.1. Ask guest about sugar 5.3.2. Add sugar to taste Plan 5.3 5.3.1 if wanted 5.3.2 1.1. Fill kettle 1.2. Put kettle on hob 1.3. Turn on and light gas 1.4. Wait for kettle to boil 1.5. Turn off gas

  9. HTA for making lots of cups of tea Plan 5 (pour tea) NO empty cups ? for each guest 5.3 5.1 5.2 YES

  10. Types of plan • Fixed sequence • Optional tasks • Waiting for events • Cycles • Time sharing • Discretionary • Mixtures

  11. Knowledge-based analysis • Listing of all objects and actions involved in task • Building taxonomies • One technique: • task analysis for knowledge description (TAKD) • Task descriptive hierarchy (TDH)

  12. Knowledge-based analysis: example Kitchen item OR preparation mixing bowl, plate, chopping board cooking frying pan, casserole, saucepan dining plate, soup bowl, casserole, glass

  13. Knowledge-based analysis: exampleTAKD Kitchen item AND /_ shape XOR / |_ dished / | mixing bowl, casserole, sauce pan, soup bowl, glass / |_ flat / plate, chopping board, frying pan /_ function OR {_ preparation { mixing bowl, plate, chopping board {_ cooking { frying pan, casserole, sauce pan {_ dining XOR |_ for food | plate, soup bowl, casserole |_ for drink glass

  14. Knowledge-based analysis: exampleTDH for actions Kitchen job OR |__ preparation | beating, mixing |__ cooking | frying, boiling, baking |__ dining pouring, eating, drinking

  15. Sources for task analysis • Documentation • Domain expert opinion • Direct observation

  16. Task analysis related tointerface design • Never complete • Should not be the sole arbiter of interface style and structure

  17. 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.)

  18. User Interface • Locus of interaction • Cushioning buffer • Visible aspect of the invisible system

  19. Design Effective Interfaces Basic questions: • Who is the user? • What is the task? • What is the environment in which the system will operate?

  20. Designer Guidance I • Measurable human factors • time to learn • speed of performance • rate of errors • retention over time • subjective satisfaction • Often forced tradeoffs

  21. Designer Guidance II • High-level theories and models • Middle-level principles • Specific and practical guidelines

  22. 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. 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

  24. High-level theories III • Consistency/Completenes 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”

  25. 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

  26. OAI model

  27. Understand the user • Physical abilities and physical workplaces • Cognitive and perceptual abilities • Personality differences • Cultural and international diversity • Users with disabilities • Elderly users

  28. The Notion of Task in HCIDraper, 1993 • Problematic notion: a task is not the same thing to all people in all circumstances (e.g. preparing a business letter) • Plea in favour of prototyping cycle for task analysis: task analysis -> design product -> build prototype -> evaluate

  29. Testing of accomplishments of design goals • Pilot studies • Expert reviews • Usability tests • Acceptance tests

  30. Summary • Task analysis • “Know thy user” • Recording task objects and actions • Construction of suitable interface objects and actions • Extensive testing • Iterative refinement

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