CS2341

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CS2341

• Lecture 5 Task Analysis
• Robert Stevens
• http//www.cs.man.ac.uk/stevensr

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Introduction

• The way people perform tasks with current
  systems real world and virtual
• Decomposition of tasks into sub-tasks
• Classification of tasks knowledge
• Listing of objects used and actions performed
• Methodology
• TA and Activity Diagrams

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Task Analysis Basics

• Analysis of how people perform their jobs the
  things they use, the actions they take and the
  things they need to know
• In order to clean a house
• Find vacuum cleaner and tools
• Clean rooms that need to be cleaned
• Empty dustbag when full
• Put cleaner and tools away
• Need to know about state of rooms, locations of
  tools, operation of tools, etc.
• Strictly, should not include why people perform
  tasks
• The observable things that users do, but why
  included at a shallow level
• About existing systems production of training
  materials
• Used for clarification of task organisation and
  knowledge when designing a new system

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Three Kinds of Task Analysis

• Hierarchical task analysis How tasks are split
  into sub-tasks, their ordering and when they are
  performed
• Classification of Task Knowledge What users need
  to know about a task and how that knowledge is
  organised
• Entity Relationship analysis An object based
  approach, concentrating upon Actors and objects
  they use, the relationships between them and the
  actions performed
• Different emphases and intentions

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Scope

• Scope of TA wide
• As well as a system, it will include surrounding
  objects, actions, actors and tasks
• In word processing, will include maintaining
  printers, using filing cabinets, reference
  material, etc.
• Many of these will never be part of any system
• Establishes contexts of use
• In TA the user is central
• Similar to Activity Diagrams

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Hierarchical Task Analysis

• Decomposition of a task like clean the house
  into sub-tasks
• Those sub-tasks further decomposed
• Form a task hierarchy
• Gives ordering of tasks
• Plans give further instructions Choice, disjoint
  paths
• Formed from the viewpoint of one Actor, but other
  actors included in task names and plans
• Activity Diagrams organise and emphasise
  differently

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Cleaning a House

• 0. in order to clean the 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 any of 3.1, 3.2, 3.3 in any order,
  depending on which rooms need cleaning.

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Hierarchical Task Analysis (HTA)

• Task Decomposition
• Numbers indicate levels of task
• Plans give extra information about tasks Choice,
  concurrency, order, etc.
• Plan 3 describes tasks 3.1, 3.2, 3.3 and 3.4
• Underlining decomposition ended
• Need stop condition
• Textual and diagrammatic forms

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Cleaning a house (2)

• Plan 0 tells us emptying bag done at any point
  the conditional is expressed at a higher level
• If we only noticed a full bag during cleaning,
  the task would within task 3
• Not all rooms need to be cleaned
• Rooms may be cleaned in any order
• Cleaning orientated varnishing or washing floor
  would indicate the hall to be done last
• A more sophisticated plan 3 could indicate
  different routines

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Stopping Rules

• When does one stop modelling?
• Sending nerve signals and flexing muscles?
• Catabolising glucose to provide energy?
• The formation of petroleum that will make
  plastics?
• Cost benefit analysis what is the cost of
  modelling something?
• If P(mistake) Cost(mistake) lt threshold, then
  dont model
• Avoid cognitive activities, muscle actions,
• But be aware of what you are modelling for
• Number of mouse clicks can be important!

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Making Tea

• Boil water
• Empty pot
• Make pot
• Wait 4 5 mins (brewing)
• Pour tea
• Plan 0 do 1 at same if pot dirty, do 2 after 1
  do 3 and 4 then do 5.

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Making Tea (1)
Pouring a round of tea for n people
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More About Making Tea

• Which tasks need to be expanded?
• Emptying pot and brewing need no decomposition
• I fill the kettle, put it on the hob and when it
  is boiling I turn off the gas
• No mention of turning gas on look for symmetry
  of tasks
• Are we talking of one cup of tea per person or an
  arbitrary number?
• Does our description of 5 (previously) fit into
  the general scheme of making a pot of tea?

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Making Tea(2)
Plan 0. do 1 at the same time, if the pot is
full 2 then 3-4 after 4/5 minutes do 5
0.make cups of tea
NO
1.boil water
2.empty pot
3.make pot
4.wait 4 or 5 minutes
5.pour tea
empty cups?
for each guest 5.3
5.1
5.2
YES
Plan 1 1.1 1.2 1.3 1.4 when kettle
boils, 1.5
5.1 put milk in cup
5.2 fill cup with tea
5.3 do sugar
Plan 3 3.1 3.2 3.3
Plan 5.3 5.3.1 if wanted 5.3.2
3.3 pour in boiling water
3.1 warm pot
3.2 put tea leaves in pot
5.3.1 ask guest about sugar
5.3.2add sugar to taste
1.1 fill Kettle
1.2 put kettle on stove
1.3 turn on and light gas
1.4 wait for kettle to boil
1.5 turn off gas
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Making Tea (3)

• Empty pot could be part of make pot
• However, 2 can be concurrent with 1, but 3 make
  pot depends on 1
• Similarly, 5 pour tea is dependent on 4 wait 4
  5 mins
• So, have these tasks at same level, despite
  differences in granularity
• What about warming pot?

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Methodology

• Documentation is a cheap way of gathering tasks
  and objects
• Beware manuals etc. can mislead
• Manuals etc. often give a perfect view, but can
  give initial view
• Observation interview techniques are important
• It is like requirements gathering
• Verbs and nouns give things and relationships
• Like class diagram modelling
• Use outliners to draw hierarchy
• Card sorting can be used to build taxonomy
• Use intermediate TA to show to expert to reveal
  more information
• An iterative process

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Task Analysis Activity Diagrams

• Task Analysis Actions, actors and objects
• Activity diagrams capture same notions.
• but different intentions
• Events explicit, immutable order, no cycles in
  Activity Diagrams
• Activity diagrams less detail a high level view
• Could write Diagrams for finer granularities, but
  roles of actors (swim-lanes) and how they
  interact a higher level, organisational aspect is
  emphasised

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Activity Diagram for House Cleaning
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Activity Diagram for Cleaning Rooms
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Uses of HTA

• Application requirements Can use TA as starting
  point for system requirements
• N.B. TA scope is very wide, but shows what should
  be supported and describes how a task is
  currently performed
• Tutorials and manuals gives chapters, sections
  etc. and their order. The document matches the
  task
• Dialogue design e.g. Menus The functions are
  grouped according to task and good terms are
  used for the labels

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Tea Making Tutorial

• Section in a tea-making tutorial
• Boiling the Water
• Preparing the Pot
• Making the Pot
• Brewing the Tea
• Pouring the Tea

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PowerPoint Menus

• Menu Bar has a collection of task oriented groups
  (File, Edit, View, Window, etc.)
• File menu has file related tasks
• Open dialogue models file opening task finding,
  naming, giving type, etc.

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Summary

• Describing the current state of the world
• Actors, actions and objects and their involvement
  in a task
• Decomposition of a task into sub-tasks
• Tasks and their plans
• Representation, and stopping rules
• Requirements, manuals and dialogue design