ceng 394 introduction to human-computer interaction
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CENG 394 Introduction to Human-Computer Interaction. CENG 394 HCI Task Analysis. Focus Analysis. Interaction design driven by what is wanted Analysis of tasks and knowledge informs: functionality and objects offered in interface; organisation (layout, grouping, navigation). - PowerPoint PPT PresentationTRANSCRIPT
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CENG 394Introduction to Human-Computer Interaction
CENG 394HCITask Analysis
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Focus Analysis
Interaction design driven by what is wanted Analysis of tasks and knowledge informs:
functionality and objects offered in interface; organisation (layout, grouping, navigation).
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What is Task Analysis?
Task Analysis is the study of the way people perform their jobs.
Methods to analyse people's jobs:what people do
what things they work with
what they must know
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What is Task Analysis? Task Analysis is the study of the way people perform
their jobs. Methods to analyse people's jobs:
what people do
what things they work with
what they must know Task analysis gathers both declarative and
procedural knowledge Declarative: objects and relationships Procedural: task sequences, goals and subgoals Also dependencies and constraints
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What is Task Analysis? Task Analysis is the study of the way people perform their jobs. Methods to analyse people's jobs:
what people do what things they work with what they must know
Task analysis gathers both declarative and procedural knowledge Declarative: objects and relationships Procedural: task sequences, goals and subgoals Also dependencies and constraints
Originally a tool for writing training manuals, now used more widely in business process analysis
http://www.atilim.edu.tr/~nergiz/SAM_0879.AVI
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An Example
must know about: vacuum cleaners, their attachments, dust bags,
cupboards, rooms etc.
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An Example
•Items related by proximity and boundaries
•Layout suggestsorder, but doesn’timpose it
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Approaches to task analysis
Task decomposition splitting task into (ordered) subtasks
Knowledge based techniques what the user knows about the task
and how it is organized
Entity/object based analysis relationships between objects, actions and the
people who perform them
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General method for Task analysis
observe
collect unstructured lists of words and actions
organize using notation or diagrams
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Differences from other techniques
Systems analysis vs. Task analysis
system design - focus - the user
Cognitive models vs. Task analysis
internal mental state - focus - external actions
practiced `unit' task - focus - whole job
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Task Decomposition
Aims:describe the actions people dostructure them within task subtask hierarchydescribe order of subtasks
Variants:Hierarchical Task Analysis (HTA)
most common
CTT ConcurTaskTrees (CNUCE, Pisa)uses LOTOS temporal operators
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Textual HTA description
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Textual HTA description
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Generating the hierarchy
1 get list of tasks
2 group tasks into higher level tasks
3 decompose lowest level tasks further
Stopping rulesHow do we know when to stop?Is “empty the dust bag” simple enough?Purpose: expand only relevant tasksMotor actions: lowest sensible level
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Tasks as explanation
imagine asking the user the question:what are you doing now?
for the same action the answer may be:typing ctrl-Bmaking a word boldemphasising a wordediting a documentwriting a letterpreparing a legal case
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parse scenario using HTA
0. in order to clean the house 1. get the vacuum cleaner out 2. get 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 vacuum cleaner and attachments away
get out cleanerfix carpet headclean dinning roomclean main bedroomempty dustbagclean sitting roomput cleaner away
1.
2.
3.2.
3.3.
3.2.
3.
4.
5.
0.
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Diagrammatic HTA
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Refining the description
Given initial HTA (textual or diagram)
How to check / improve it?
Some heuristics:paired actions e.g., where is `turn on gas'
restructure e.g., generate task `make pot'
balance e.g., is `pour tea' simpler than making pot?
generalise e.g., make one cup ….. or more
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Refined HTA for making tea
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Types of planfixed sequence - 1.1 then 1.2 then 1.3
optional tasks - if the pot is full 2
wait for events - when kettle boils 1.4
cycles - do 5.1 5.2 while there are still empty cups
time-sharing - do 1; at the same time ...
discretionary - do any of 3.1, 3.2 or 3.3 in any order
mixtures - most plans involve several of the above
Most plans use several of these.
Waiting can be considered: a task — for “busy” waits, e.g. making tea part of the plan — end is the event, e.g. email reply received
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waiting …
is waiting part of a plan?… or a task?
generally task – if ‘busy’ wait
you are actively waiting
plan – if end of delay is the event e.g. “when alarm rings”, “when reply arrives”
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Knowledge Based AnalysesAim to understand knowledge required for a
task provide training material, how-to manuals; take advantage of common knowledge across
tasks
Focus on: Objects – used in task Actions – performed
+ Use Taxonomies –represent levels of abstraction
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Knowledge Based AnalysesAim to understand knowledge required for a task
provide training material, how-to manuals; take advantage of common knowledge across tasks
Focus on: Objects – used in task Actions – performed
+ Use Taxonomies –represent levels of abstraction
Declarative knowledge elicitation techniques: established convention, existing documentation asking users to list objects; card sorting structured interviews, listing nouns and verbs
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Knowledge–Based Example …
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Knowledge–Based Example …
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Task Description HierarchyTask Analysis for Knowledge Description (TAKD) uses three types of branches in TDH taxonomies:
XOR — object in exactly one branch
AND— object must be in both
OR— can be in one, many or none
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Larger TDH example
kitchen item AND/____shape XOR/ |____dished mixing bowl, casserole, saucepan,/ | soup bowl, glass/ |____flat plate, chopping board, frying pan/____function OR {____preparation mixing bowl, plate, chopping
board {____cooking frying pan, casserole, saucepan {____dining XOR |____for food plate, soup bowl, casserole |____for drink glass
N.B. ‘/|{’ used for branch types.
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More on TDHUniqueness rule:
can the diagram distinguish all objects? If not, may consider adding extra classifiers
e.g., plate is:kitchen item/shape(flat)/function{preparation,dining(for food)}/
nothing else fits this description
Actions have taxonomy too:kitchen job OR|____ preparation beating, mixing|____ cooking frying, boiling, baking|____ dining pouring, eating, drinking
Compare taxonomies to restructure/find omissions- Objects often more easily observed than tasks! Notice: TDH decomposes by similarity, HTA byhow-to
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Abstraction and cuts
After producing detailed taxonomy‘cut’ to yield abstract view
That is, ignore lower level nodese.g. cutting above shape and below dining, plate becomes:
kitchen item/function{preparation,dining}/
This is a term in Knowledge Representation Grammar (KRG)
These can be more complex:e.g. ‘beating in a mixing bowl’ becomes:
kitchen job(preparation) using akitchen item/function{preparation}/
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Sources of Information
Documentation N.B. manuals say what is supposed to happen
but, good for key words and prompting interviews
Observation formal/informal, laboratory/field (see Chapter 9)
Interviews the expert: manager or worker? (ask both!)
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Early analysis
Extraction from transcripts list nouns (objects) and verbs (actions) beware technical language and context:
`the rain poured’ vs. `I poured the tea’
Sorting and classifying grouping or arranging words on cards ranking objects/actions for task relevance (see ch. 9) use commercial outliner
Iterative process: data sources analysis… but costly, so use cheap sources where available
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Uses – manuals & documentation
Conceptual Manual from knowledge or entity–relations based analysis good for open ended tasks
Procedural ‘How to do it’ Manual from HTA description good for novices assumes all tasks known
To make cups of tea
boil water –– see page 2empty potmake pot –– see page 3wait 4 or 5 minutespour tea –– see page 4
–– page 1 ––
Make pot of tea
warm potput tea leaves in potpour in boiling water
–– page 3 ––
once water has boiled
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Uses – requirements & design For documentation:How To manual
useful for novices assumes all tasks known
Requirements capture and design lifts focus from system to use suggests candidates for automation may uncover user’s conceptual model
Detailed interface design taxonomies suggest menu layout object/action lists suggest interface objects task frequency guides default choices existing task sequences guide dialogue design
Task analysis can be continually iterated to improve and enhance