Task Analysis
Formal Methods
for
Interactive Systems
Part 3 — Task Analysis
Antonio Cerone
United Nations University
International Institute for Software Technology
Macau SAR China
email: antonio@iist.unu.edu
web: www.iist.unu.edu
A. Cerone, UNU-IIST – p.1/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Tasks and Task Analysis
Task: the activity that has to be performed to
achieve a goal
A. Cerone, UNU-IIST – p.2/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Tasks and Task Analysis
Task: the activity that has to be performed to
achieve a goal
Task Analysis:
the process of analysing the way people perform
tasks:
•
what people do
•
what things they work with
•
what they must know
A. Cerone, UNU-IIST – p.2/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Method for Task analysis
General Method
•
observe the user’s behaviour
•
collect unstructured lists of words and actions
•
organise using notation or diagrams
A. Cerone, UNU-IIST – p.3/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Method for Task analysis
General Method
•
observe the user’s behaviour
•
collect unstructured lists of words and actions
•
organise using notation or diagrams
Focus on the user’s objective obsevable
behaviour rather than on the user’s internal
mental model
A. Cerone, UNU-IIST – p.3/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Method for Task analysis
General Method
•
observe the user’s behaviour
•
collect unstructured lists of words and actions
•
organise using notation or diagrams
Focus on the user’s objective obsevable
behaviour rather than on the user’s internal
mental model
However, it might involve building a conceptual
model
A. Cerone, UNU-IIST – p.3/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Purpose of Task Analysis
•
production of training material and
documentation
A. Cerone, UNU-IIST – p.4/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Purpose of Task Analysis
•
•
production of training material and
documentation
contribute to the design of a new system
• building a conceptual model
• generation of user interfaces
A. Cerone, UNU-IIST – p.4/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Approaches to Task Analysis
Three different approaches:
A. Cerone, UNU-IIST – p.5/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Approaches to Task Analysis
Three different approaches:
•
task decomposition
•
knowledge-based techniques
•
entity-relationship-based analysis
A. Cerone, UNU-IIST – p.5/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Task Decomposition
•
describe the actions people do
•
structure them within task-subtask hierarchy
•
describe order of subtasks
A. Cerone, UNU-IIST – p.6/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Task Decomposition
•
describe the actions people do
•
structure them within task-subtask hierarchy
•
describe order of subtasks
Hierarchical Task Analysis (HTA)
•
text and diagrams to show hierarchy
•
plans to describe order
A. Cerone, UNU-IIST – p.6/38
What | Task Decomposition | Task Knowledge | Task ER | Use
HTA: Textual Notation
Hierarchy description:
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 5 minutes
6. pour tea
A. Cerone, UNU-IIST – p.7/38
What | Task Decomposition | Task Knowledge | Task ER | Use
HTA: Textual Notation
Hierarchy description:
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 5 minutes
6. pour tea
Plans
Plan 0.
do 1
at the same time, if pot is full do 2
then do 3 – 4 – 5
after 5 minutes do 6
A. Cerone, UNU-IIST – p.7/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Generating the Hierarchy
•
get list of tasks
•
group tasks into higher level tasks
•
decompose lower level tasks further
A. Cerone, UNU-IIST – p.8/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Generating the Hierarchy
•
get list of tasks
•
group tasks into higher level tasks
•
decompose lower level tasks further
How to know when to stop?
A. Cerone, UNU-IIST – p.8/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Generating the Hierarchy
•
get list of tasks
•
group tasks into higher level tasks
•
decompose lower level tasks further
How to know when to stop?
Stopping rules:
•
Simplicity: Is the task simple enough?
•
Purpose: Is the task relevant?
•
Motor Action: lowest sensible level
A. Cerone, UNU-IIST – p.8/38
What | Task Decomposition | Task Knowledge | Task ER | Use
HTA: Diagrammatic Notation
0.
make a cup
of tea
1.
2.
boil water
empty pot
3.
put tea leaves
in pot
plan 0.
do 1
at the same time, if pot is full do 2
then do 3 – 4 – 5
after 5 minutes do 6
4.
pour in
boiling water
5.
wait 5 minutes
6.
pour tea
A. Cerone, UNU-IIST – p.9/38
What | Task Decomposition | Task Knowledge | Task ER | Use
HTA: Decomposition
0.
make a cup
of tea
1.
2.
boil water
empty pot
3.
put tea leaves
in pot
plan 0.
do 1
at the same time, if pot is full do 2
then do 3 – 4 – 5
after 5 minutes do 6
4.
pour in
boiling water
5.
wait 5 minutes
6.
pour tea
A. Cerone, UNU-IIST – p.10/38
What | Task Decomposition | Task Knowledge | Task ER | Use
HTA: Decomposition
0.
make a cup
of tea
1.
2.
boil water
empty pot
plan 0.
do 1
at the same time, if pot is full do 2
then do 3 – 4 – 5
after 5 minutes do 6
3.
put tea leaves
in pot
4.
1.3.
1.4.
turn off gas
pour in
boiling water
5.
wait 5 minutes
6.
pour tea
plan 1.
do 1.1 – 1.2 – 1.3
when kettle boils do 1.5
1.1.
fill kettle
1.2.
put kettle
on stove
wait for kettle
to boil
A. Cerone, UNU-IIST – p.10/38
What | Task Decomposition | Task Knowledge | Task ER | Use
HTA: Domain Expert
0.
make a cup
of tea
1.
2.
boil water
empty pot
3.
put tea leaves
in pot
plan 0.
do 1
at the same time, if pot is full do 2
then do 3 – 4 – 5
after 5 minutes do 6
4.
pour in
boiling water
5.
wait 5 minutes
6.
pour tea
plan 1.
do 1.1 – 1.2 – 1.3
when kettle boils do 1.5
Looking for errors
Describe the step in the task hierarchy
to a domain expert
1.1.
fill kettle
1.2.
put kettle
on stove
1.3.
wait for kettle
to boil
1.4.
turn off gas
A. Cerone, UNU-IIST – p.11/38
What | Task Decomposition | Task Knowledge | Task ER | Use
HTA: Domain Expert
0.
make a cup
of tea
1.
2.
boil water
empty pot
3.
put tea leaves
in pot
plan 0.
do 1
at the same time, if pot is full do 2
then do 3 – 4 – 5
after 5 minutes do 6
4.
pour in
boiling water
5.
wait 5 minutes
6.
pour tea
plan 1.
do 1.1 – 1.2 – 1.3
when kettle boils do 1.5
Looking for errors
Describe the step in the task hierarchy
to a domain expert
We forgot to warm the pot
1.1.
fill kettle
1.2.
put kettle
on stove
1.3.
wait for kettle
to boil
1.4.
turn off gas
A. Cerone, UNU-IIST – p.11/38
What | Task Decomposition | Task Knowledge | Task ER | Use
HTA: Domain Expert
0.
make a cup
of tea
1.
2.
boil water
empty pot
plan 1.
do 1.1 – 1.2 – 1.3
when kettle boils do 1.5
3.
put tea leaves
in pot
plan 0.
do 1
at the same time, if pot is full do 2
then do 3 – 4 – 5
after 5 minutes do 6
4.
pour in
boiling water
5.
wait 5 minutes
6.
pour tea
6
Looking for errors
Describe the step in the task hierarchy
to a domain expert
We forgot to warm the pot
1.1.
fill kettle
1.2.
put kettle
on stove
1.3.
wait for kettle
to boil
1.4.
turn off gas
A. Cerone, UNU-IIST – p.11/38
What | Task Decomposition | Task Knowledge | Task ER | Use
HTA: Omissions
0.
make a cup
of tea
1.
2.
boil water
3.
empty pot
warm pot
plan 0.
do 1
at the same time, if pot is full do 2
then do 3 – 4 – 5 – 6
after 5 minutes do 7
4.
put tea leaves
in pot
5.
pour in
boiling water
6.
wait 5 minutes
7.
pour tea
plan 1.
do 1.1 – 1.2 – 1.3
when kettle boils do 1.5
1.1.
fill kettle
1.2.
put kettle
on stove
1.3.
wait for kettle
to boil
1.4.
turn off gas
A. Cerone, UNU-IIST – p.12/38
What | Task Decomposition | Task Knowledge | Task ER | Use
HTA: Omissions
0.
make a cup
of tea
1.
2.
boil water
3.
empty pot
warm pot
plan 0.
do 1
at the same time, if pot is full do 2
then do 3 – 4 – 5 – 6
after 5 minutes do 7
4.
put tea leaves
in pot
5.
pour in
boiling water
6.
wait 5 minutes
7.
pour tea
plan 1.
do 1.1 – 1.2 – 1.3
when kettle boils do 1.5
Omissions?
1.1.
fill kettle
1.2.
put kettle
on stove
1.3.
wait for kettle
to boil
1.4.
turn off gas
A. Cerone, UNU-IIST – p.12/38
What | Task Decomposition | Task Knowledge | Task ER | Use
HTA: Omissions
0.
make a cup
of tea
1.
2.
boil water
3.
empty pot
warm pot
plan 0.
do 1
at the same time, if pot is full do 2
then do 3 – 4 – 5 – 6
after 5 minutes do 7
4.
put tea leaves
in pot
5.
pour in
boiling water
6.
wait 5 minutes
7.
pour tea
plan 1.
do 1.1 – 1.2 – 1.3
when kettle boils do 1.5
Omissions?
1.1.
fill kettle
1.2.
put kettle
on stove
1.3.
wait for kettle
to boil
'
1.4.
turn off gas
$
A. Cerone, UNU-IIST – p.12/38
What | Task Decomposition | Task Knowledge | Task ER | Use
HTA: Omissions
0.
make a cup
of tea
1.
2.
boil water
3.
empty pot
warm pot
plan 0.
do 1
at the same time, if pot is full do 2
then do 3 – 4 – 5 – 6
after 5 minutes do 7
4.
put tea leaves
in pot
5.
pour in
boiling water
6.
wait 5 minutes
7.
pour tea
plan 1.
do 1.1 – 1.2 – 1.3
when kettle boils do 1.5
Omissions?
Where do we turn the gas on?
1.1.
fill kettle
1.2.
put kettle
on stove
1.3.
wait for kettle
to boil
'
1.4.
turn off gas
$
A. Cerone, UNU-IIST – p.12/38
What | Task Decomposition | Task Knowledge | Task ER | Use
HTA: Omissions
0.
make a cup
of tea
1.
2.
boil water
3.
empty pot
warm pot
plan 0.
do 1
at the same time, if pot is full do 2
then do 3 – 4 – 5 – 6
after 5 minutes do 7
4.
put tea leaves
in pot
5.
pour in
boiling water
6.
wait 5 minutes
7.
pour tea
plan 1.
do 1.1 – 1.2 – 1.3
when kettle boils do 1.5
Omissions?
Where do we turn the gas on?
Maybe implicit in
1.1.
fill kettle
?
'
1.2.
put kettle
on stove
$'
1.3.
wait for kettle
to boil
1.4.
turn off gas
$
A. Cerone, UNU-IIST – p.12/38
What | Task Decomposition | Task Knowledge | Task ER | Use
HTA: Omissions
0.
make a cup
of tea
1.
2.
boil water
3.
empty pot
warm pot
plan 0.
do 1
at the same time, if pot is full do 2
then do 3 – 4 – 5 – 6
after 5 minutes do 7
4.
put tea leaves
in pot
5.
pour in
boiling water
6.
wait 5 minutes
7.
pour tea
plan 1.
do 1.1 – 1.2 – 1.3
when kettle boils do 1.5
Omissions?
Where do we turn the gas on?
We make it explicit here
?
1.1.
fill kettle
1.2.
put kettle
on stove
1.3.
wait for kettle
to boil
'
1.4.
turn off gas
$
A. Cerone, UNU-IIST – p.12/38
What | Task Decomposition | Task Knowledge | Task ER | Use
HTA: Umbalanced Hierarchy
0.
make a cup
of tea
1.
2.
boil water
3.
empty pot
warm pot
plan 0.
do 1
at the same time, if pot is full do 2
then do 3 – 4 – 5 – 6
after 5 minutes do 7
4.
put tea leaves
in pot
5.
1.4.
1.5.
turn off gas
pour in
boiling water
6.
wait 5 minutes
7.
pour tea
plan 1.
do 1.1 – 1.2 – 1.3
when kettle boils do 1.5
1.1.
fill kettle
1.2.
put kettle
on stove
1.3.
turn on and
light gas
wait for kettle
to boil
A. Cerone, UNU-IIST – p.13/38
What | Task Decomposition | Task Knowledge | Task ER | Use
HTA: Umbalanced Hierarchy
0.
make a cup
of tea
1.
2.
boil water
3.
empty pot
warm pot
plan 0.
do 1
at the same time, if pot is full do 2
then do 3 – 4 – 5 – 6
after 5 minutes do 7
4.
put tea leaves
in pot
5.
pour in
boiling water
6.
wait 5 minutes
7.
pour tea
plan 1.
do 1.1 – 1.2 – 1.3
when kettle boils do 1.5
Why is the hierarchy unbalanced?
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
A. Cerone, UNU-IIST – p.13/38
What | Task Decomposition | Task Knowledge | Task ER | Use
HTA: Umbalanced Hierarchy
0.
make a cup
of tea
1.
2.
boil water
3.
empty pot
warm pot
plan 0.
do 1
at the same time, if pot is full do 2
then do 3 – 4 – 5 – 6
after 5 minutes do 7
4.
put tea leaves
in pot
5.
pour in
boiling water
6.
wait 5 minutes
7.
pour tea
plan 1.
do 1.1 – 1.2 – 1.3
when kettle boils do 1.5
Why is the hierarchy unbalanced?
Maybe too many details at the high level
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
A. Cerone, UNU-IIST – p.13/38
What | Task Decomposition | Task Knowledge | Task ER | Use
HTA: Umbalanced Hierarchy
0.
make a cup
of tea
1.
2.
boil water
'
3.
empty pot
plan 1.
do 1.1 – 1.2 – 1.3
when kettle boils do 1.5
warm pot
&
plan 0.
do 1
at the same time, if pot is full do 2
then do 3 – 4 – 5 – 6
after 5 minutes do 7
4.
put tea leaves
in pot
5.
pour in
boiling water
$
6.
wait 5 minutes
7.
pour tea
%
Why is the hierarchy unbalanced?
Maybe too many details at the high level
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
A. Cerone, UNU-IIST – p.13/38
What | Task Decomposition | Task Knowledge | Task ER | Use
HTA: Umbalanced Hierarchy
0.
make a cup
of tea
1.
2.
boil water
'
3.
empty pot
plan 1.
do 1.1 – 1.2 – 1.3
when kettle boils do 1.5
warm pot
&
plan 0.
do 1
at the same time, if pot is full do 2
then do 3 – 4 – 5 – 6
after 5 minutes do 7
4.
put tea leaves
in pot
5.
pour in
boiling water
$
6.
wait 5 minutes
7.
pour tea
%
Why is the hierarchy unbalanced?
Maybe too many details at the high level
We add new make pot node which
encompass tasks 3, 4, 5. Why not 2 and 6?
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
A. Cerone, UNU-IIST – p.13/38
What | Task Decomposition | Task Knowledge | Task ER | Use
HTA: Further Decompositions
0.
make a cup
of tea
1.
2.
boil water
3.
empty pot
plan 0.
do 1
at the same time, if pot is full do 2
then do 3 – 4
after 5 minutes do 5
4.
make pot
wait 5 minutes
5.
pour tea
plan 1.
do 1.1 – 1.2 – 1.3
when kettle boils do 1.5
plan 3.
do 3.1 – 3.2 – 3.3
1.1.
fill kettle
3.1.
warm pot
3.2.
1.2.
put kettle
on stove
1.3.
put tea
leaves in pot
turn on and
light gas
3.3.
pour in
boiling water
1.4.
wait for kettle
to boil
1.5.
turn off gas
A. Cerone, UNU-IIST – p.14/38
What | Task Decomposition | Task Knowledge | Task ER | Use
HTA: Further Decompositions
0.
make a cup
of tea
1.
2.
boil water
3.
empty pot
plan 0.
do 1
at the same time, if pot is full do 2
then do 3 – 4
after 5 minutes do 5
'
4.
make pot
5.
wait 5 minutes
basic
basic
plan 1.
do 1.1 – 1.2 – 1.3
when kettle boils do 1.5
$
pour tea
&
%
plan 3.
do 3.1 – 3.2 – 3.3
1.1.
fill kettle
3.1.
warm pot
3.2.
1.2.
put kettle
on stove
1.3.
put tea
leaves in pot
turn on and
light gas
3.3.
pour in
boiling water
1.4.
wait for kettle
to boil
1.5.
turn off gas
A. Cerone, UNU-IIST – p.14/38
What | Task Decomposition | Task Knowledge | Task ER | Use
HTA: Further Decompositions
0.
make a cup
of tea
1.
2.
boil water
3.
empty pot
plan 0.
do 1
at the same time, if pot is full do 2
then do 3 – 4
after 5 minutes do 5
'
4.
make pot
5.
wait 5 minutes
5.1.
plan 5. %
&
3.1.
warm pot
3.2.
1.2.
put kettle
on stove
1.3.
put tea
leaves in pot
turn on and
light gas
5.2.
put milk
in cup
plan 3.
do 3.1 – 3.2 – 3.3
fill kettle
pour tea
do 5.1 – 5.2
if desired do 5.3
plan 1.
do 1.1 – 1.2 – 1.3
when kettle boils do 1.5
1.1.
$
fill cup
with tea
5.3.
add sugar
3.3.
pour in
boiling water
1.4.
wait for kettle
to boil
1.5.
turn off gas
A. Cerone, UNU-IIST – p.14/38
What | Task Decomposition | Task Knowledge | Task ER | Use
'
HTA: Iteration
0.
make a cup
of tea
&
1.
2.
boil water
3.
empty pot
$
plan 0.
do 1
at the same time, if pot is full do 2
then do 3 – 4
after 5 minutes do 5
%
4.
make pot
5.
wait 5 minutes
pour tea
plan 5.
do 5.1 – 5.2
if desired do 5.3
plan 1.
do 1.1 – 1.2 – 1.3
when kettle boils do 1.5
5.1.
plan 3.
do 3.1 – 3.2 – 3.3
1.1.
fill kettle
3.1.
warm pot
3.2.
1.2.
put kettle
on stove
1.3.
put tea
leaves in pot
turn on and
light gas
5.2.
put milk
in cup
fill cup
with tea
5.3.
add sugar
3.3.
pour in
boiling water
1.4.
wait for kettle
to boil
1.5.
turn off gas
A. Cerone, UNU-IIST – p.15/38
What | Task Decomposition | Task Knowledge | Task ER | Use
HTA: Iteration
0.
make cups
of tea
1.
2.
boil water
3.
empty pot
plan 0.
do 1
at the same time, if pot is full do 2
then do 3 – 4
after 5 minutes do 5
4.
make pot
5.
wait 5 minutes
pour tea
plan 5.
do 5.1 – 5.2
if desired do 5.3
plan 1.
do 1.1 – 1.2 – 1.3
when kettle boils do 1.5
5.1.
plan 3.
do 3.1 – 3.2 – 3.3
1.1.
fill kettle
3.1.
warm pot
3.2.
1.2.
put kettle
on stove
1.3.
put tea
leaves in pot
turn on and
light gas
5.2.
put milk
in cup
fill cup
with tea
5.3.
add sugar
3.3.
pour in
boiling water
1.4.
wait for kettle
to boil
1.5.
turn off gas
A. Cerone, UNU-IIST – p.15/38
What | Task Decomposition | Task Knowledge | Task ER | Use
HTA: Iteration
0.
make cups
of tea
1.
2.
boil water
3.
empty pot
plan 0.
do 1
at the same time, if pot is full do 2
then do 3 – 4
after 5 minutes do 5
4.
make pot
plan 5.
5.
wait 5 minutes
pour tea
plan 1.
do 1.1 – 1.2 – 1.3
when kettle boils do 1.5
5.1.
plan 3.
do 3.1 – 3.2 – 3.3
1.1.
fill kettle
3.1.
warm pot
3.2.
1.2.
put kettle
on stove
1.3.
put tea
leaves in pot
turn on and
light gas
5.2.
put milk
in cup
fill cup
with tea
3.3.
pour in
boiling water
1.4.
wait for kettle
to boil
for each guest
do 5.3
5.1
- 5.2 -
6
NO
empty
cups?
6
'
$
&
%
5.3.
add sugar
YES
1.5.
turn off gas
A. Cerone, UNU-IIST – p.15/38
What | Task Decomposition | Task Knowledge | Task ER | Use
HTA: Final Decomposition
0.
make cups
of tea
1.
2.
boil water
3.
empty pot
plan 0.
do 1
at the same time, if pot is full do 2
then do 3 – 4
after 5 minutes do 5
4.
make pot
plan 5.
5.
wait 5 minutes
pour tea
5.1.
3.1.
warm pot
3.2.
1.2.
put kettle
on stove
1.3.
put tea
leaves in pot
turn on and
light gas
5.2.
put milk
in cup
plan 3.
do 3.1 – 3.2 – 3.3
fill kettle
5.1
- 5.2 -
6
plan 1.
do 1.1 – 1.2 – 1.3 – 1.4
when kettle boils do 1.5
1.1.
for each guest
do 5.3
3.3.
pour in
boiling water
1.4.
wait for kettle
to boil
fill cup
with tea
6
NO
empty
cups?
YES
5.3.
do sugar
5.3.1.
ask guest
about sugar
plan 5.3.
do 5.3.1 – if wanted 5.3.2
5.3.2.
add sugar
to taste
1.5.
turn off gas
A. Cerone, UNU-IIST – p.16/38
What | Task Decomposition | Task Knowledge | Task ER | Use
HTA: Fixed Sequence
0.
make cups
of tea
1.
2.
boil water
3.
empty pot
plan 0.
do 1
at the same time, if pot is full do 2
then do 3 – 4
after 5 minutes do 5
4.
make pot
plan 5.
5.
wait 5 minutes
pour tea
5.1.
3.1.
warm pot
3.2.
1.2.
put kettle
on stove
1.3.
put tea
leaves in pot
turn on and
light gas
5.2.
put milk
in cup
plan 3.
do 3.1 – 3.2 – 3.3
fill kettle
5.1
- 5.2 -
6
plan 1.
do 1.1 – 1.2 – 1.3 – 1.4
when kettle boils do 1.5
1.1.
for each guest
do 5.3
3.3.
pour in
boiling water
1.4.
wait for kettle
to boil
fill cup
with tea
6
NO
empty
cups?
YES
5.3.
do sugar
5.3.1.
ask guest
about sugar
plan 5.3.
do 5.3.1 – if wanted 5.3.2
5.3.2.
add sugar
to taste
1.5.
turn off gas
A. Cerone, UNU-IIST – p.17/38
What | Task Decomposition | Task Knowledge | Task ER | Use
HTA: Optional Tasks
0.
make cups
of tea
1.
2.
boil water
3.
empty pot
plan 0.
do 1
at the same time, if pot is full do 2
then do 3 – 4
after 5 minutes do 5
4.
make pot
plan 5.
5.
wait 5 minutes
pour tea
5.1.
3.1.
warm pot
3.2.
1.2.
put kettle
on stove
1.3.
put tea
leaves in pot
turn on and
light gas
5.2.
put milk
in cup
plan 3.
do 3.1 – 3.2 – 3.3
fill kettle
5.1
- 5.2 -
6
plan 1.
do 1.1 – 1.2 – 1.3 – 1.4
when kettle boils do 1.5
1.1.
for each guest
do 5.3
3.3.
pour in
boiling water
1.4.
wait for kettle
to boil
fill cup
with tea
6
NO
empty
cups?
YES
5.3.
do sugar
5.3.1.
ask guest
about sugar
plan 5.3.
do 5.3.1 – if wanted 5.3.2
5.3.2.
add sugar
to taste
1.5.
turn off gas
A. Cerone, UNU-IIST – p.18/38
What | Task Decomposition | Task Knowledge | Task ER | Use
HTA: Waiting for Events
0.
make cups
of tea
1.
2.
boil water
3.
empty pot
plan 0.
do 1
at the same time, if pot is full do 2
then do 3 – 4
after 5 minutes do 5
4.
make pot
plan 5.
5.
wait 5 minutes
pour tea
5.1.
3.1.
warm pot
3.2.
1.2.
put kettle
on stove
1.3.
put tea
leaves in pot
turn on and
light gas
5.2.
put milk
in cup
plan 3.
do 3.1 – 3.2 – 3.3
fill kettle
5.1
- 5.2 -
6
plan 1.
do 1.1 – 1.2 – 1.3 – 1.4
when kettle boils do 1.5
1.1.
for each guest
do 5.3
3.3.
pour in
boiling water
1.4.
wait for kettle
to boil
fill cup
with tea
6
NO
empty
cups?
YES
5.3.
do sugar
5.3.1.
ask guest
about sugar
plan 5.3.
do 5.3.1 – if wanted 5.3.2
5.3.2.
add sugar
to taste
1.5.
turn off gas
A. Cerone, UNU-IIST – p.19/38
What | Task Decomposition | Task Knowledge | Task ER | Use
HTA: Cycles
0.
make cups
of tea
1.
2.
boil water
3.
empty pot
plan 0.
do 1
at the same time, if pot is full do 2
then do 3 – 4
after 5 minutes do 5
4.
make pot
plan 5.
5.
wait 5 minutes
pour tea
5.1.
3.1.
warm pot
3.2.
1.2.
put kettle
on stove
1.3.
put tea
leaves in pot
turn on and
light gas
5.2.
put milk
in cup
plan 3.
do 3.1 – 3.2 – 3.3
fill kettle
5.1
- 5.2 -
6
plan 1.
do 1.1 – 1.2 – 1.3 – 1.4
when kettle boils do 1.5
1.1.
for each guest
do 5.3
3.3.
pour in
boiling water
1.4.
wait for kettle
to boil
fill cup
with tea
6
NO
empty
cups?
YES
5.3.
do sugar
5.3.1.
ask guest
about sugar
plan 5.3.
do 5.3.1 – if wanted 5.3.2
5.3.2.
add sugar
to taste
1.5.
turn off gas
A. Cerone, UNU-IIST – p.20/38
What | Task Decomposition | Task Knowledge | Task ER | Use
HTA: Time-sharing
0.
make cups
of tea
1.
2.
boil water
3.
empty pot
plan 0.
do 1
at the same time, if pot is full do 2
then do 3 – 4
after 5 minutes do 5
4.
make pot
plan 5.
5.
wait 5 minutes
pour tea
5.1.
3.1.
warm pot
3.2.
1.2.
put kettle
on stove
1.3.
put tea
leaves in pot
turn on and
light gas
5.2.
put milk
in cup
plan 3.
do 3.1 – 3.2 – 3.3
fill kettle
5.1
- 5.2 -
6
plan 1.
do 1.1 – 1.2 – 1.3 – 1.4
when kettle boils do 1.5
1.1.
for each guest
do 5.3
3.3.
pour in
boiling water
1.4.
wait for kettle
to boil
fill cup
with tea
6
NO
empty
cups?
YES
5.3.
do sugar
5.3.1.
ask guest
about sugar
plan 5.3.
do 5.3.1 – if wanted 5.3.2
5.3.2.
add sugar
to taste
1.5.
turn off gas
A. Cerone, UNU-IIST – p.21/38
What | Task Decomposition | Task Knowledge | Task ER | Use
HTA: Mixtures
0.
make cups
of tea
1.
2.
boil water
3.
empty pot
plan 0.
do 1
at the same time, if pot is full do 2
then do 3 – 4
after 5 minutes do 5
4.
make pot
plan 5.
5.
wait 5 minutes
pour tea
5.1.
3.1.
warm pot
3.2.
1.2.
put kettle
on stove
1.3.
put tea
leaves in pot
turn on and
light gas
5.2.
put milk
in cup
plan 3.
do 3.1 – 3.2 – 3.3
fill kettle
5.1
- 5.2 -
6
plan 1.
do 1.1 – 1.2 – 1.3 – 1.4
when kettle boils do 1.5
1.1.
for each guest
do 5.3
3.3.
pour in
boiling water
1.4.
wait for kettle
to boil
fill cup
with tea
6
NO
empty
cups?
YES
5.3.
do sugar
5.3.1.
ask guest
about sugar
plan 5.3.
do 5.3.1 – if wanted 5.3.2
5.3.2.
add sugar
to taste
1.5.
turn off gas
A. Cerone, UNU-IIST – p.22/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Decomposition Heuristics
•
•
•
paired actions
e.g., turn on and turn on gas
restructure/balance e.g., generate make pot
and decompose pour tea
generalise
e.g., from make a cup of tea to make cups of
tea
A. Cerone, UNU-IIST – p.23/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Knowledge-based Analysis
•
list objects used in tasks
•
list actions performed
•
build taxomomies of them
A. Cerone, UNU-IIST – p.24/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Knowledge-based Analysis
•
list objects used in tasks
•
list actions performed
•
build taxomomies of them
Aim
•
•
•
to understand knowledge needed to perform a
task
=⇒ help in production of teaching material
=⇒ assess the amount of common knowledge
between different tasks
A. Cerone, UNU-IIST – p.24/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Knowledge-based Analysis
•
list objects used in tasks
•
list actions performed
•
build taxomomies of them
Aim
•
•
to understand knowledge needed to perform a
task
=⇒ help in production of teaching material
=⇒ assess the amount of common knowledge
between different tasks
Technique: Task Analysis for Knowledge Description — TAKD
•
A. Cerone, UNU-IIST – p.24/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Example: Kitchen Items
kitchen items
preparation
bowl, plate, chopping board
cooking
frying pan, casserole, saucepan
dining
plate, soup bowl, casserole, glass
A. Cerone, UNU-IIST – p.25/38
What | Task Decomposition | Task Knowledge | Task ER | Use
TDH notation
TDH — Task Descriptive Hierarchy
kitchen item OR
{___ preparation
{
bowl, plate, chopping board
{___ cooking
{
frying pan, casserole, saucepan
{___ dining
plate, soup bowl, casserole, glass
A. Cerone, UNU-IIST – p.26/38
What | Task Decomposition | Task Knowledge | Task ER | Use
TDH notation
TDH — Task Descriptive Hierarchy
kitchen item OR
{___ preparation
{
bowl, plate, chopping board
{___ cooking
{
frying pan, casserole, saucepan
{___ dining
plate, soup bowl, casserole, glass
Uniqueness Rule:
A complete TDH can distinguish any two
specific objects
A. Cerone, UNU-IIST – p.26/38
What | Task Decomposition | Task Knowledge | Task ER | Use
TDH notation
TDH — Task Descriptive Hierarchy
kitchen item OR
{___ preparation
{
bowl, plate, chopping board
{___ cooking
{
frying pan, casserole, saucepan
{___ dining
plate, soup bowl, casserole, glass
Uniqueness Rule:
A complete TDH can distinguish any two
specific objects
A. Cerone, UNU-IIST – p.26/38
What | Task Decomposition | Task Knowledge | Task ER | Use
TDH: Branching Type
kitchen item AND
/___ function OR
/
{___ preparation
/
{
bowl, plate, chopping board
/
{___ cooking
/
{
frying pan, casserole, saucepan
/
{___ dining XOR
/
|___ for food
/
|
plate, soup bowl, casserole
/
|___ for drink
/
glass
/___ shape XOR
...
A. Cerone, UNU-IIST – p.27/38
What | Task Decomposition | Task Knowledge | Task ER | Use
TDH: Branching Type
kitchen item AND
/___ function OR
/
{___ preparation
/
{
bowl, plate, chopping board
/
{___ cooking
/
{
frying pan, casserole, saucepan
/
{___ dining XOR
/
|___ for food
/
|
plate, soup bowl, casserole
/
|___ for drink
/
glass
/___ shape XOR
...
kitchen item/function{dining(for food)/shape(dished)}/
KRG — Knowledge Representation Grammar
A. Cerone, UNU-IIST – p.27/38
What | Task Decomposition | Task Knowledge | Task ER | Use
TDH: Branching Type
kitchen item AND
/___ function OR
/
{___ preparation
/
{
bowl, plate, chopping board
/
{___ cooking
/
{
frying pan, casserole, saucepan
/
{___ dining XOR
/
|___ for food
/
|
plate, soup bowl, casserole
/
|___ for drink
/
glass
/___ shape XOR
...
kitchen item/function{dining(for drink)/shape(dished)}/
KRG — Knowledge Representation Grammar
A. Cerone, UNU-IIST – p.27/38
What | Task Decomposition | Task Knowledge | Task ER | Use
TDH: Branching Type
kitchen item AND
/___ function OR
/
{___ preparation
/
{
bowl, plate, chopping board
/
{___ cooking
/
{
frying pan, casserole, saucepan
/
{___ dining XOR
/
|___ for food
/
|
plate, soup bowl, casserole
/
|___ for drink
/
glass
/___ shape XOR
...
kitchen item/function{preparation,dining(for food)/shape(flat)}/
A. Cerone, UNU-IIST – p.27/38
KRG — Knowledge Representation Grammar
What | Task Decomposition | Task Knowledge | Task ER | Use
Taxomomy of Actions
kitchen job OR
{___ preparation
{
beating, mixing
{___ cooking
{
frying, boiling, baking
{___ dining
pouring, eating, drinking
A. Cerone, UNU-IIST – p.28/38
What | Task Decomposition | Task Knowledge | Task ER | Use
ER-based techniques
Entity-Relationship Based Techniques
•
list objects used in tasks
•
list actions performed
•
define relationships between object and
actions
A. Cerone, UNU-IIST – p.29/38
What | Task Decomposition | Task Knowledge | Task ER | Use
ER-based techniques
Entity-Relationship Based Techniques
•
list objects used in tasks
•
list actions performed
•
•
•
•
define relationships between object and
actions
similar to techniques used in database and
OO
but includes non-computer entities
emphasis on domain understanding rather
than implementation
A. Cerone, UNU-IIST – p.29/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Example: Vera’s Veggies
•
Vera’s Veggies a market gardening firm
•
owner/manager: Vera
•
employes: Sam and Tony
•
tools include a tractor Fergie
•
two fields and a glasshouse
•
new computer controlled irrigation system
A. Cerone, UNU-IIST – p.30/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Object Classification
•
concrete objects
simple things: spade, plough, glasshouse
A. Cerone, UNU-IIST – p.31/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Object Classification
•
•
concrete objects
simple things: spade, plough, glasshouse
actors
human: Vera, Sam, Tony, the customers
A. Cerone, UNU-IIST – p.31/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Object Classification
•
•
concrete objects
simple things: spade, plough, glasshouse
actors
human: Vera, Sam, Tony, the customers
non-human: irrigation system
A. Cerone, UNU-IIST – p.31/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Object Classification
•
•
•
concrete objects
simple things: spade, plough, glasshouse
actors
human: Vera, Sam, Tony, the customers
non-human: irrigation system
composite objects
sets: the team = Vera, Sam, Tony
A. Cerone, UNU-IIST – p.31/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Object Classification
•
•
•
concrete objects
simple things: spade, plough, glasshouse
actors
human: Vera, Sam, Tony, the customers
non-human: irrigation system
composite objects
sets: the team = Vera, Sam, Tony
tuples: tractor = < Fergie, plough>
A. Cerone, UNU-IIST – p.31/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Attributes
An irrigation pump may have:
•
status: on/off/faulty
•
capacity: 100 litres/minute
A. Cerone, UNU-IIST – p.32/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Attributes
An irrigation pump may have:
•
status: on/off/faulty
•
capacity: 100 litres/minute
However, emphasis on object participation in
tasks:
•
•
keep only relevant attributes (e.g., status)
no need for completeness, but convenient to
be initially overinclusive and drop
unnecessary attributes later
A. Cerone, UNU-IIST – p.32/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Actions
Agent performs Action to change Patient
A. Cerone, UNU-IIST – p.33/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Actions
Agent performs Action to change Patient
Sam
planted
the leeks
A. Cerone, UNU-IIST – p.33/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Actions
Agent performs Action to change Patient
Sam
planted
using Instrument
the leeks
A. Cerone, UNU-IIST – p.33/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Actions
Agent performs Action to change Patient
Sam
planted
the leeks
Tony
dug
the field
using Instrument
with
the spade
A. Cerone, UNU-IIST – p.33/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Actions
Agent performs Action to change Patient
using Instrument
Sam
planted
the leeks
Tony
dug
the field
Vera
turns on
the irrigation system
with
the spade
A. Cerone, UNU-IIST – p.33/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Actions
Agent performs Action to change Patient
using Instrument
Sam
planted
the leeks
Tony
dug
the field
Vera
turns on
the irrigation system
with
the spade
irrigation system is turned on
(control)
(automatically)
A. Cerone, UNU-IIST – p.33/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Actions
Agent performs Action to change Patient
using Instrument
Sam
planted
the leeks
Tony
dug
the field
Vera
turns on
the irrigation system
with
the spade
irrigation system is turned on
(control)
(automatically)
Vera
(indirect agent)
programmed
the irrigation system
...
A. Cerone, UNU-IIST – p.33/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Actions
Agent performs Action to change Patient
using Instrument
Sam
planted
the leeks
Tony
dug
the field
Vera
turns on
the irrigation system
with
the spade
irrigation system is turned on
(control)
(automatically)
Vera
(indirect agent)
programmed
the irrigation system
Vera
(message)
told
Sam
to
...
...
A. Cerone, UNU-IIST – p.33/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Actions
Agent performs Action to change Patient
using Instrument
Sam
planted
the leeks
Tony
dug
the field
Vera
turns on
the irrigation system
with
the spade
irrigation system is turned on
(control)
(automatically)
Vera
(indirect agent)
programmed
the irrigation system
Vera
(message)
told
Sam
Vera as worker
...
Vera as manager
...
to
...
...
(agents may act in several roles)
A. Cerone, UNU-IIST – p.33/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Object and Actions
Object Sam human actor
Actions:
S1: drive tractor
S2: dig carrots
A. Cerone, UNU-IIST – p.34/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Object and Actions
Object Sam human actor
Actions:
S1: drive tractor
S2: dig carrots
Object Vera human actor | the proprietor
Actions: as worker
V1: plant marrow seed
V2: programme irrigation controller
Actions: as manager
V3: tell sam to dig the carrots
A. Cerone, UNU-IIST – p.34/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Object and Actions
Object Sam human actor
Actions:
S1: drive tractor
S2: dig carrots
Object Vera human actor | the proprietor
Actions: as worker
V1: plant marrow seed
V2: programme irrigation controller
Actions: as manager
V3: tell sam to dig the carrots
Object the men composite
Comprises: Sam, Tony
A. Cerone, UNU-IIST – p.34/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Object and Actions
Object Sam human actor
Actions:
S1: drive tractor
S2: dig carrots
Object Vera human actor | the proprietor
Actions: as worker
V1: plant marrow seed
V2: programme irrigation controller
Actions: as manager
V3: tell sam to dig the carrots
Object the men composite
Comprises: Sam, Tony
Object glasshouse simple
Attribute: humidity: 0–100%
A. Cerone, UNU-IIST – p.34/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Object and Actions
Object Sam human actor
Actions:
S1: drive tractor
S2: dig carrots
Object Vera human actor | the proprietor
Actions: as worker
V1: plant marrow seed
V2: programme irrigation controller
Actions: as manager
V3: tell sam to dig the carrots
Object the men composite
Comprises: Sam, Tony
Object glasshouse simple
Attribute: humidity: 0–100%
Object Irrigation Controller non-human
Actions:
IC1: turn on Pump 1
IC2: turn on Pump 2
IC3: turn on Pump 3
A. Cerone, UNU-IIST – p.34/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Events
•
performing of an action
Sam dug the carrots
A. Cerone, UNU-IIST – p.35/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Events
•
•
performing of an action
Sam dug the carrots
spontaneous events
the marrow seeds germinated
A. Cerone, UNU-IIST – p.35/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Events
•
•
performing of an action
Sam dug the carrots
spontaneous events
the marrow seeds germinated
the humidity drops below 25%
A. Cerone, UNU-IIST – p.35/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Events
•
•
•
performing of an action
Sam dug the carrots
spontaneous events
the marrow seeds germinated
the humidity drops below 25%
timed events
at midnight
A. Cerone, UNU-IIST – p.35/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Relationships
Object Marrow simple
Actions:
M1: germinate
M2: grow
A. Cerone, UNU-IIST – p.36/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Relationships
Object Marrow simple
Actions:
M1: germinate
M2: grow
Events
Ev1: humidity drops below 25%
Ev2: midnight
A. Cerone, UNU-IIST – p.36/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Relationships
Object Marrow simple
Actions:
M1: germinate
M2: grow
Events
Ev1: humidity drops below 25%
Ev2: midnight
Relations object-object
location ( Pump 1, glasshouse )
A. Cerone, UNU-IIST – p.36/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Relationships
Object Marrow simple
Actions:
M1: germinate
M2: grow
Events
Ev1: humidity drops below 25%
Ev2: midnight
Relations object-object
location ( Pump 1, glasshouse )
Relation action-object
patient ( V3, Sam )
— Vera tells Sam to dig
patient ( S2, the carrots )
— Sam digs the carrots ...
instrument ( S2, spade )
— ... with the spade
A. Cerone, UNU-IIST – p.36/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Relations action-event
Relations action-event
before ( V1, M1 )
— the marrow must be sown before it can germinate
before ( M1, M2 )
— the marrow must germinate before it can grow
V1: plant marrow seed
M1: germinate
M2: grow
A. Cerone, UNU-IIST – p.37/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Relations action-event
Relations action-event
before ( V1, M1 )
— the marrow must be sown before it can germinate
before ( M1, M2 )
— the marrow must germinate before it can grow
triggers ( Ev2, IC1 )
— when it is midnight the control turns on Pump 1
Ev1: humidity drops below 25%
IC1: turn on Pump 1
A. Cerone, UNU-IIST – p.37/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Relations action-event
Relations action-event
before ( V1, M1 )
— the marrow must be sown before it can germinate
before ( M1, M2 )
— the marrow must germinate before it can grow
triggers ( Ev2, IC1 )
— when it is midnight the control turns on Pump 1
causes ( V2, IC1 )
— the controller turns on Pump1
because Vera programmed it
V2: programme irrigation controller
IC1: turn on Pump 1
A. Cerone, UNU-IIST – p.37/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Relations action-event
Relations action-event
before ( V1, M1 )
— the marrow must be sown before it can germinate
before ( M1, M2 )
— the marrow must germinate before it can grow
triggers ( Ev2, IC1 )
— when it is midnight the control turns on Pump 1
causes ( V2, IC1 )
— the controller turns on Pump1
because Vera programmed it
causes ( V3, S2 )
— Sam digs the carrots
because Vera told him to do so
V3: tell sam to dig the carrots
S2: dig carrots
A. Cerone, UNU-IIST – p.37/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Relations action-event
Relations action-event
before ( V1, M1 )
— the marrow must be sown before it can germinate
before ( M1, M2 )
— the marrow must germinate before it can grow
triggers ( Ev2, IC1 )
— when it is midnight the control turns on Pump 1
causes ( V2, IC1 )
— the controller turns on Pump1
because Vera programmed it
causes ( V3, S2 )
— Sam digs the carrots
because Vera told him to do so
Ordering of events better described using HTA
either to analyse order of subtasks and actions
annotated with objects
or to represent the life-cycle of a specific object
A. Cerone, UNU-IIST – p.37/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Uses of Task Analysis
Purposes:
•
requirement capture and system design
• lift focus from system to use
• suggest candidates for automation
• uncover user’s conceptual model
A. Cerone, UNU-IIST – p.38/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Uses of Task Analysis
Purposes:
•
•
requirement capture and system design
• lift focus from system to use
• suggest candidates for automation
• uncover user’s conceptual model
interface design
• taxonomies suggest menu layout
• object/action lists suggest interface objects
• task frequency guides default choices
• task sequences guide dialogue design
A. Cerone, UNU-IIST – p.38/38
What | Task Decomposition | Task Knowledge | Task ER | Use
Uses of Task Analysis
Purposes:
•
•
•
requirement capture and system design
• lift focus from system to use
• suggest candidates for automation
• uncover user’s conceptual model
interface design
• taxonomies suggest menu layout
• object/action lists suggest interface objects
• task frequency guides default choices
• task sequences guide dialogue design
documentation and teaching
A. Cerone, UNU-IIST – p.38/38
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