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Light Switch Issues

Consistency – The switch design is inconsistent with common light switches

Visibility – No visible cue regarding on/off operation Affordance – The switch design does not suggest how

should it be operated

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How do people use an InterfaceLecture # 4

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User Interface Design?

Design is solving a problem Design is creating an object or the means to enable, in

our case a user, to achieve an intent To optimize our solution we need to understand how

people interact with the world

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Human ActionIntent

Plan

Act

Assess

Refine/Stop

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Norman’s Activity Model

Don Norman (1988) proposed that users view the user-interface as a mean to an end

The interface, according to Norman’s model provides users with the mechanisms to achieve something that they desire or want

This mechanism includes 2 basic elements An Interface – The means used to communicates between

the user and application what needs to be done Interaction – The mechanism by which the user is expected

to achieve the tasks using the interface

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User Interface Design For the example below

The interface includes: The blue icon Message Labeled button

The interaction includes: Reading the message Clicking on the close button

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The Action Model The action model deals with the interaction It suggests that the way people act can be decomposed

into: An Intention A Plan An action An Evaluation

Actions are performed within a context of a higher level goal

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Example – Removing The Error Message

To remove the error message (Goal) the Activity Model hypothesizes that user will Formulate an intent to close the message View the box and decide that to close it one needs to click

on the close button Click on the “Close” button Check to make sure that the dialog box

is indeed closed

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Activity ModelGoal

External World

Execution Gap

Evaluation GapHow do I (the user) affect the state of the world

Was the change that I sensed the same as what I expected

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Gulf of Execution

Deals with the gap between what the user wants to do – Intention and the action needed to implement the intent How do I start my car How do I save a document How do I set the time on my car clock

The role of the user interface is to help bridge this gap by helping users determe how to act

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Gulf of Evaluation

Deals with the gap between perception and interpretation Did my car started? Was my document saved? Am I controlling the time on my car clock?

The role of the user interface is to help user determine what happened in the real world

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Implementing the Action For the user Interface to be effective it will need to assist

users in helping them Execution

Form an intention Plan out the action – how will it flow Execute the plan

Evaluation Perceive the result Interpret the result Evaluate the result

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Form an intention

Plan out the action Execute the plan

Perceive the result

Interpret the result

Evaluate the result

Veering to the Left of the Road

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Closing the GapsHelping the user cross the chasm

Goal

Intention

Detailed Plan

Comparison

Interpretation

Perception

External World

Execution

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Example - Execution• Forming a Goal

• I want to inform my team about a meeting I had.

• Intention to Act• I have outlook open on my desktop. I will set up a meeting

for the team and myself. I will open a meeting invitation

• Planning the Action• I need to move the cursor to the meeting icon and click on it

• Executing the Action• I move the cursor to the meeting icon and I click on it

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Example - Evaluation

• Feedback from the Action• A meeting set up form is opened

• Interpret the Feedback• I am now able able to specify a meeting and invite Sean

• Evaluate the Outcome• Positive – I’m able to start scheduling a meeting. No further

action is needed• Negative – The form I opened is for scheduling an

appointment not a meeting• The Action Cycle is either repeated or a new goal is formed

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Example – Planning Challenge

From Michael J. Darnell @ http://www.baddesigns.com/

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Example – Planning Challenge

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Example – Execution Challenge

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Example – Interpretation Challenge

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So what are the the implication of this model for design?