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  • Learning outcomesAt the end of this lecture, you should be able to:Draft the Hierarchical Task Analysis (chart or textual based)

  • Key termsTask analysisHierarchical task analysis

  • Task Analysis - Whats a Task?A set of human actions that contributes to a functional objective and to the goal of the system. Scope or size of a task is determined by the definition of the objectives. Each task should be approximately equal in size.But not always the case

  • Task - Decomposition

  • Task - DecompositionGoal - state of the system that a human wants to accomplish. Task - activities required, used, or deemed necessary to achieve a goal.Actions - steps required to complete the task.

  • Task AnalysisA method/set of methods for understanding the tasks users carry out with a product/systemTo analyze the underlying rationale and purpose of what people are doing; what are they trying to achieve, why are they trying to achieve it, and how are they going about it?To investigate an existing situationCan be used for many different purposes within design and evaluation activities

  • Task AnalysisKey definitions (Norman, 1988): Goal - the state that the human wishes to achieve Task - the activity required in order to bring about the state the human wishes to achieve (the goal)

  • Task AnalysisTask analysis techniques support user-centred design Informs us (in detail) as to: how users use existing products how users may interact with future productsCan be used to: improve current design identify potential problems with new design identify requirements for new design design training materials and manuals develop evaluation plans

  • Hierarchical Task AnalysisHTA is a commonly used means of breaking tasks down into a hierarchy of goals, operations (actions) and plansIt involves breaking a task down into subtasks and then into sub subtasksThese are then grouped together as plans that specify how the tasks might be performed in an actual situation

  • Procedure for carrying out HTAThe starting point is a user goal, then examined the main tasks associated with achieving that goal. Where appropriate, these tasks are subdivided into subtasksStart with the overall goal (verb-noun pair), e.g. Use email, Print a letterBreak these down into meaningful sub goals/tasks (asking how question)Break down sub goals further until reach an appropriate stopping point

  • Procedure for carrying out HTAAdd plans to the analysis - conditional statements, often utilizing Boolean logic, e.g.DO 1, THEN 2, THEN (IF condition = true) DO 3, ELSE DO 4, THEN EXITRepresent the goals, sub goals, operations and plans using either:graphical views (boxes and arrows)non-graphical methods (e.g. tabulation, outlines, textual)

  • HTA Structure Chart Notation

  • Stages of a HTAStarting the analysisSpecify the main task.Break down main task into 4-8 subtask, and specify in terms of objectives. Cover the whole area of interestDraw out as layered plans, logically & technically correct. None should be missing.

  • Stages of a HTAProgressing the analysisDecide on level of detail and stop decomposition. Should be consistent between tasks. Can range from detailed to high level description.Decide if a depth first or breadth first decomposition should be done. Can alternate between the two.Label and number the HTA.

  • Stages of a HTAFinalizing the analysis.Check that decomposition and numbering is consistent. May produce a written account of the processes.Have a second person look it over. They should know the tasks but not be involved in the analysis.

  • HTA Graphical view

  • HTA Graphical view

  • HTA Textual representationHTA can also be written as a list like this: 0. to clean house 1. get vacuum cleaner 2. clean rooms 2.1 clean hall 2.2 clean living rooms 2.3 clean bedrooms etc 3. empty dust bag 4. put vacuum cleaner away Plan 0: do 1,2,4 when dust bag full, do 3 Plan 2: do any of 2.1, 2.2, 2.3 in any order depending on which rooms need cleaning.

  • An example of HTA for a Microwave OvenWhat is the overall goal? Cook food! How is this done? Prepare meal Put meal in oven Select programme Listen for bell to ring Remove meal

  • An example of HTA for a Microwave OvenSelecting a programme - How is this done? Set to auto sensor Set to defrost Set timer to cookWhat are the rules that influence the order in which tasks/subtasks take place? (the plans)

  • An example of HTA for a Microwave Oven

  • Further Task Analysis (Matrixes)

  • Task Analysis Critical thinkingSome requirements that might have emerged from carrying out this Task Analysis:The need for a distinctive, but not annoying, bell soundThe need for an easily accessible mechanism for opening the doorThe need for a highly learnable (guessable) means of selecting a programmed

  • Assumptions about the interfaceMust be made to fulfill the system requirements.Very true if we are describing how users behave on an existing system.Should not be made when we are designing a new system.Dont limit our options before we start.

  • Q &A