Performing User Interface Design

The Golden Rules

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The Golden Rules

1. Place the user in control2. Reduce the user’s memory load3. Make the interface consistent

Place the User in Control

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Place the User in Control

• Define interaction modes in a way that does not force a user into unnecessary or undesired actions• Provide for flexible interaction• Allow user interaction to be interruptible and undoable• Streamline interaction as skill levels advance and allow the interaction

to be customized• Hide technical internals from the casual user• Design for direct interaction with objects that appear on the screen

Reduce the User’s Memory Load

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Reduce the User’s Memory Load

• Reduce demand on short-term memory• Establish meaningful defaults• Define shortcuts that are intuitive• The visual layout of the interface should be based on a real world

metaphor• Disclose information in a progressive fashion

Make the Interface Consistent

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Make the Interface Consistent

• Allow the user to put the current task into a meaningful context• Maintain consistency across a family of applications• If past interactive models have created user expectations, do not

make changes unless there is a compelling reason to do so

User Interface Analysis and Design

Interface Analysis and Design ModelsFour different models come into play:• User model• Design model• Mental model / system perception• Implementation model

The Process

1. User, task, and environment analysis and modeling2. Interface design3. Interface construction (implementation)4. Interface validation

User Analysis

• Are users trained professionals, technicians, or workers?• What level of formal education average user has?• Are users capable of self-learning or require classroom training?• What is the age range of the user community?• Will users be represented by one gender?• Do users work office hours or until work is done?• What is the primary spoken language among users?• What are the consequences of making a mistake?

User Analysis

• User interviews• Sales input• Marketing input• Support input

Task Analysis and Modeling

Goal of task analysis is to answer the following questions:• What work will the user perform?• What tasks and subtasks will be performed?• What specific problem domain objects will the user manipulate?• What is the sequence of tasks (workflow)?• What is the hierarchy of tasks?

Task Analysis and Modeling

• Use-cases• Task elaboration• Object elaboration• Workflow analysis• Hierarchical representation

Analysis of Display Content

Questions that need to be answered:• Are different types of data are assigned to different location on

screen?• Can user customize screen location for content?• How is a large report partitioned for ease of understanding?• Will graphical output be scaled to fit within display?• How error messages will be presented?

Analysis of the Work Environment

• Will system be placed in a user-friendly location?• Will two or more people share information?• Is proper lighting present?• Keyboard / mouse access?

Interface Design Steps

1. Using information developed during interface analysis, define interface objects and actions

2. Define events (user actions) that will cause the state of the user interface to change

3. Depict each interface state and it will actually look to the end-user4. Indicate how the user interprets the state of the system from

information provided through the interface

Design Issues

• Response time• Help facilities• Error handling• Menu and command labeling• Application accessibility• Internationalization

Design Evaluation

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