◦ Goals, Tasks, and Actions
 Task Characteristics: The Nature of the Work
 Task Sequences: There May Be More Than One Way to Do a
Task

Goal: the end result to be achieved

Task: structured set of related activities that are
undertaken in some sequence

Action: an individual operation or step that
needs to be undertaken as part of the task.
UIDE Chapter 4

All humans subdivide Goals into tasks; and
tasks are subdivided into separate actions
UIDE Chapter 4
Norman suggests that users engage in seven
stages of activity.
These stages
span the gulfs
of evaluation
and execution
shown in next
slide.
first
cycle
1. Establish the goal
2. Form the intention
3. Specify the action sequence
4. Execute the action
5. Perceive the system state
6. Interpret the system state
7. Evaluate the system state
with respect to the goals and
intentions
UIDE Chapter 4
second
cycle
third cycle


The gulf of execution, that Norman describes, is
where the user knows what needs to be achieved,
the user has a goal, but does not know which
physical variables to adjust, or in what way to
adjust them.
The gulf of evaluation is where the system has
altered, usually as a result of user’s action, but
the user cannot easily understand the change in
the system’s state. In other words, it is difficult
for the user to work out what has happened to
the system, and whether the change fits in with
the initial goals and intentions.
UIDE Chapter 4
Goals and intentions: A goal is the state the person wishes to achieve; an
intention is the decision to act so as to achieve the goal.
Specification of the action sequence: The psychological process of determining
the psychological representation of the actions that are to be executed by the
user on the mechanisms of the system.
Mapping from psychological goals and intentions to action sequence: In order to
specify the action sequence, the user must translate the psychological goals and
intentions into the desired system state, then determine what settings of the
control mechanisms will yield that state, and then determine what physical
manipulations of the mechanisms are required. The result is the internal, mental
specification of the actions that are to be executed.
Physical state of the system: The physical state of the system, determined by the
value of all its physical variables.
Control Mechanisms: The physical devices that control the physical variables.
Mapping between the physical mechanisms and system state: The relationship
between the settings of the mechanisms of the system and the system state.
Interpretation of system state: The relationship between the physical state of the
system and the psychological goals of the user can only be determined by first
translating the physical state into psychological states (perception), then
interpreting the perceived system state in terms of the psychological variables of
interest.
Evaluating the outcome: Evaluation of the system state requires comparing the
interpretation of the perceived system state with the desired goals. This often
leads to a new set of goals and intentions
UIDE Chapter 4
The Goals, Operators, Methods, and Selection rules (GOMS) model was developed
by Card, Moran and Newell in the mid-1970’s (Card et al., 1980; 1983). The
GOMS model has four components: Goals, Operators, Methods, and Selection
rules. Card et al. (1980) describe these components in the following way:
Goals: “ A goal is a symbolic structure that defines a state of affairs to be
achieved, and determines a set of possible methods by which it may be
accomplished.”
Operators: “ Operators are elementary motor or information-processing acts,
whose execution is necessary to change any aspect of the user’s memory or to
affect the task environment.”
Methods: “ A method describes a procedure for accomplishing a goal. The
description of the procedure is cast as a continual sequence of goals and
operators, with conditional tests on the contents of the user’s immediate memory
and on the state of the task environment.”
Selection rules: “ When a goal is attempted, there may be more than one method
available to the user to accomplish the goal.”
UIDE Chapter 4
Four Levels of Cognition.
 1. Conceptual Level
 2. Semantic Level
 3. Syntactical Level
 4. Lexical Level
UIDE Chapter 4








Variety of tasks
Frequency of tasks
Knowledge and skill required
Environmental factors
Time critical
Safety hazards
Will user work alone or with others
User normally switches between several
tasks
UIDE Chapter 4


Granularity – levels of detail
Work-flow
UIDE Chapter 4
◦ Task Analysis
 Clues for Improving Design: Problems and Difficulties
with the Current UI
 Analyze errors
 Find “work around”
 Observe job aids, reference manuals, etc.
 Artifacts – object or aid
 Techniques for Task Analysis


Describe what is to be done
Describe how a user does the task
 Describing How to Do It: Scenarios and Use Cases
 Cognitive Task Analysis: Moving from Scenarios and
Use Cases to Cognitive Walkthrough
UIDE Chapter 4
Essential Use Case
Concrete Use Case
UIDE Chapter 4


“Evaluates the steps required to perform a
task and attempts to uncover mismatches
between how the users think about a task and
how the UI designer thinks about the task”
Look at the first slide about Cognition
Models.
UIDE Chapter 4
Produce a “Cognitive
Walkthrough” of a TV or other
remote control you may have at
home.
•From “Turn ON”
•Actions in between
•To “Turn OFF”
See pp 73-75
UIDE Chapter 4

Structural Models

Functional Models

Structural versus Functional Models

The Utility of Mental Models in HCI
UIDE Chapter 4
UIDE Chapter 4
UIDE Chapter 4
 Where
Is This Work Done?
◦ The Physical Environment: Is This a Pleasant Place
to Be?
◦ The Safety Environment: Is This a Safe Place to Be?
◦ The Social Environment: Do People Help Each Other?
◦ The Organizational Environment: Does Management
Support This Work?
The User Support Environment
◦ Consideration of Environmental Aspects and How
They Affect Design
UIDE Chapter 4
 The
Two Types of Knowledge
Needed for User Interface Design
 Four
Psychological Principles
1. Users See What They Expect to See
2. Users Have Difficulty Focusing on More Than
One Activity at a Time
3. It Is Easier to Perceive a Structured Layout
4. It Is Easier to Recognize Something Than to
Recall It
UIDE Chapter 5
Design Principles - First Principles of Interactive Design website about the
principles that covers:

Aesthetics - Aesthetic design should be left to those
schooled and skilled in its application: Graphic/visual
designers

Anticipation - Bring to the user all the information and tools
needed for each step of the process

Autonomy

Color

Consistency

Defaults

Discoverability

Efficiency of the User

Explorable Interfaces

Fitts's Law

Human-Interface Objects

Latency Reduction

Learnability

Metaphors

Protect Users' Work

Readability

Simplicity

State: Track it

Visible Interfaces
Design Rules - 8 Golden Rules
1.
Strive for consistency
Design dialogs to yield closure
4.
Sequences of actions should be organized into groups with a beginning,
middle, and end. The informative feedback at the completion of a group of
actions shows the user their activity has completed successfully
Offer error prevention and simple error handling
5.
design the form so that users cannot make a serious error; for example, prefer
menu selection to form fill-in and do not allow alphabetic characters in numeric
entry fields
if users make an error, instructions should be written to detect the error and
offer simple, constructive, and specific instructions for recovery
segment long forms and send sections separately so that the user is not
penalized by having to fill the form in again - but make sure you inform the
user that multiple sections are coming up
Permit easy reversal of actions
Support internal locus of control
6.
7.
Experienced users want to be in charge. Surprising system actions, tedious
sequences of data entries, inability or difficulty in obtaining necessary
information, and inability to produce the action desired all build anxiety and
dissatisfaction
Reduce short-term memory load
8.
◦

A famous study suggests that humans can store only 7 (plus or minus 2)
pieces of information in their short term memory. You can reduce short
term memory load by designing screens where options are clearly visible,
or using pull-down menus and icons
Prevent Errors - The third principle is to prevent errors
whenever possible. Steps can be taken to design so that errors
are less likely to occur, using methods such as organizing
screens and menus functionally, designing screens to be
distinctive and making it difficult for users to commit
irreversible actions. Expect users to make errors, try to
anticipate where they will go wrong and design with those
actions in mind.
consistent sequences of actions should be required in similar situations
identical terminology should be used in prompts, menus, and help screens
consistent color, layout, capitalization, fonts, and so on should be employed
throughout.
2.
Enable frequent users to use shortcuts
to increase the pace of interaction use abbreviations, special keys, hidden
commands, and macros
3.
Offer informative feedback
for every user action, the system should respond in some way (in web design,
this can be accomplished by DHTML - for example, a button will make a clicking
sound or change color when clicked to show the user something has happened)
UIDE Chapter 5

Users See What They Expect to See
UIDE Chapter 5

Users Have Difficulty Focusing on More Than
One Activity at a Time
◦ The Cocktail Party Effect
 Principle of Perceptual Organization
 Group like things together
 Principle of Importance
 Prominent display for important items
UIDE Chapter 5

It Is Easier to Perceive a Structured Layout
UIDE Chapter 5

Gestalt principles
a.
b.
c.
d.
e.
Proximity
Similarity
Closure
Continuity
Symmetry
UIDE Chapter 5
◦ It Is Easier to Recognize Something Than to Recall It
Principle of recognition
 Knowledge in the head &
Knowledge in the world
UIDE Chapter 5
 Three
Principles from Experience:
Visibility, Affordance, and
Feedback
◦ The Principle of Visibility: It Should Be Obvious What
a Control Is Used For
UIDE Chapter 5
◦ The Principle of Affordance: It Should Be Obvious
How a Control Is Used
UIDE Chapter 5

The Principle of Feedback: It Should Be
Obvious When a Control Has Been Used
UIDE Chapter 5