Chapter 4-Finding out about tasksand work

Chapter 5 -Requirements gathering:knowledge of user

interface design

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◦ 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.

Describing Users’ Work

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Goals, Tasks, Actions All humans subdivide Goals into tasks; and

tasks are subdivided into separate actions

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  first cycle  

second cycle 

third 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

     

Norman's 7 stages of Human Cognition Thinking

Norman suggests that users engage in seven stages of activity.

These stages span the gulfs of evaluation and execution shown in next slide.

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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.

Norman’s Gulf problems

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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

Information about Norman’s stages

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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.”

GOMS Cognition Model

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Four Levels of Cognition. 1. Conceptual Level 2. Semantic Level 3. Syntactical Level 4. Lexical Level

Foley and Van Dam Model (from Computer Graphics textbook)

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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

Task Characteristics

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Granularity – levels of detail Work-flow

Task Analysis

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◦ 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

Describing Users’ Work

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Use Cases

Concrete Use Case

Essential Use Case

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“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.

Cognitive Walk-Through

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Remote

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

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Structural Models

Functional Models

Structural versus Functional Models

The Utility of Mental Models in HCI

Mental Models

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Visual aid

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Aid?

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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

Environmental Considerations:

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The Two Types of Knowledge Needed for User Interface Design

Four Psychological Principles1. 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

User Interface Design

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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 Rules1. Strive for consistency

consistent sequences of actions should be required in similar situationsidentical 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)

4. Design dialogs to yield closure 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

5. Offer error prevention and simple error handling 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 fieldsif users make an error, instructions should be written to detect the error and offer simple, constructive, and specific instructions for recoverysegment 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

6. Permit easy reversal of actions7. Support internal locus of control

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

8. Reduce short-term memory load ◦ 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.

Design Knowledge

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Users See What They Expect to See

4 Psychological Principles

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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

4 Psychological Principles

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It Is Easier to Perceive a Structured Layout

4 Psychological Principles

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Gestalt principlesa. Proximityb. Similarityc. Closured. Continuitye. Symmetry

4 Psychological Principles

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◦ It Is Easier to Recognize Something Than to Recall It

Principle of recognition Knowledge in the head & Knowledge in the world

4 Psychological Principles

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Three Principles from Experience: Visibility, Affordance, and Feedback◦ The Principle of Visibility: It Should Be

Obvious What a Control Is Used For

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◦ The Principle of Affordance: It Should Be Obvious How a Control Is Used

Three Principles from Experience: Visibility, Affordance, and Feedback

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The Principle of Feedback: It Should Be Obvious When a Control Has Been Used

Three Principles from Experience: Visibility, Affordance, and Feedback