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Chapter 12Chapter 12User Interface DesignUser Interface Design


Interface DesignInterface Design

Easy to use?Easy to use?Easy to understand?Easy to understand?

Easy to learn?Easy to learn?


Interface DesignInterface Design

lack of consistencylack of consistencytoo much memorizationtoo much memorizationno guidance / helpno guidance / helpno context sensitivityno context sensitivitypoor responsepoor responseArcane/unfriendlyArcane/unfriendly

Typical Design ErrorsTypical Design Errors


Golden RulesGolden Rules

Place the user in controlPlace the user in control Reduce the user’s memory loadReduce the user’s memory load Make the interface consistentMake the interface consistent


Place the User in ControlPlace the User in ControlDefine interaction modes in a way that does Define interaction modes in a way that does not force a user into unnecessary or not force a user into unnecessary or undesired actions. undesired actions.

Provide for flexible interaction. Provide for flexible interaction.

Allow user interaction to be interruptible Allow user interaction to be interruptible and undoable. and undoable.

Streamline interaction as skill levels Streamline interaction as skill levels advance and allow the interaction to be advance and allow the interaction to be customized. customized.

Hide technical internals from the casual Hide technical internals from the casual user. user.

Design for direct interaction with objects Design for direct interaction with objects that appear on the screen. that appear on the screen.


Reduce the User’s Memory LoadReduce the User’s Memory LoadReduce demand on short-term memory. Reduce demand on short-term memory.

Establish meaningful defaults. Establish meaningful defaults.

Define shortcuts that are intuitive. Define shortcuts that are intuitive.

The visual layout of the interface should be The visual layout of the interface should be based on a real world metaphor. based on a real world metaphor.

Disclose information in a progressive Disclose information in a progressive fashion.fashion.


Make the Interface Make the Interface ConsistentConsistent

Allow the user to put the current task into Allow the user to put the current task into a meaningful context. a meaningful context.

Maintain consistency across a family of Maintain consistency across a family of applications. applications.

If past interactive models have created If past interactive models have created user expectations, do not make changes user expectations, do not make changes unless there is a compelling reason to do unless there is a compelling reason to do so. so.


User Interface Design ModelsUser Interface Design Models

User modelUser model — a profile of all end — a profile of all end users of the systemusers of the system

Design modelDesign model — a design realization — a design realization of the user modelof the user model

Mental model (system perception)Mental model (system perception) — — the user’s mental image of what the the user’s mental image of what the interface isinterface is

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Implementation modelImplementation model — the interface “look and — the interface “look and feel” coupled with supporting information that feel” coupled with supporting information that describe interface syntax and semanticsdescribe interface syntax and semantics


User Interface Design ProcessUser Interface Design Process


Interface AnalysisInterface Analysis Interface analysis means understanding Interface analysis means understanding

– (1) the people (end-users) who will interact with the (1) the people (end-users) who will interact with the system through the interface;system through the interface;

– (2) the tasks that end-users must perform to do their (2) the tasks that end-users must perform to do their work, work,

– (3) the content that is presented as part of the (3) the content that is presented as part of the interface interface

– (4) the environment in which these tasks will be (4) the environment in which these tasks will be conducted conducted..


User AnalysisUser Analysis

Are users trained professionals, technician, clerical, or Are users trained professionals, technician, clerical, or manufacturing workers?manufacturing workers?

What level of formal education does the average user have?What level of formal education does the average user have? Are the users capable of learning from written materials or Are the users capable of learning from written materials or

have they expressed a desire for classroom training?have they expressed a desire for classroom training? Are users expert typists or keyboard phobic?Are users expert typists or keyboard phobic? What is the age range of the user community?What is the age range of the user community? Will the users be represented predominately by one gender?Will the users be represented predominately by one gender? How are users compensated for the work they perform? How are users compensated for the work they perform?

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• Do users work normal office hours or do they work until Do users work normal office hours or do they work until the job is done?the job is done?

• Is the software to be an integral part of the work users do Is the software to be an integral part of the work users do or will it be used only occasionally?or will it be used only occasionally?

• What is the primary spoken language among users?What is the primary spoken language among users?

• What are the consequences if a user makes a mistake What are the consequences if a user makes a mistake using the system?using the system?

• Are users experts in the subject matter that is addressed Are users experts in the subject matter that is addressed by the system?by the system?

• Do users want to know about the technology the sits Do users want to know about the technology the sits behind the interface?behind the interface?


Task Analysis and ModelingTask Analysis and Modeling Answers the following questions …Answers the following questions …– What work will the user perform in What work will the user perform in

specific circumstances?specific circumstances?– What tasks and subtasks will be What tasks and subtasks will be

performed as the user does the work?performed as the user does the work?– What specific problem domain objects What specific problem domain objects

will the user manipulate as work is will the user manipulate as work is performed?performed?

– What is the sequence of work tasks—What is the sequence of work tasks—the workflow?the workflow?

– What is the hierarchy of tasks?What is the hierarchy of tasks?


• Use-casesUse-cases define basic interaction define basic interaction

• Task elaborationTask elaboration refines interactive tasks refines interactive tasks

• Object elaborationObject elaboration identifies interface objects (classes) identifies interface objects (classes)

• Workflow analysisWorkflow analysis defines how a work process is defines how a work process is completed when several people (and roles) are involvedcompleted when several people (and roles) are involved


Swimlane DiagramSwimlane Diagrampatient pharmacist physician

reque sts that a prescrip tio n be re f illed

no refills remaining

checks patie nt records

dete rmines status o f prescr ip tio n

refills remaining

refill not allowed

approves refill

ev aluates alte rnativ e med icatio n

none

re ce ives request to contact physician

alternative available

checks inv entory fo r re f ill or alternative

out of stockrece iv e s o ut o f stock no tif ication

rece iv e s t ime/ date to pick up

in stock

picks up prescript io n

f ills p rescrip tion

Figure 12.2 Swimlane diagram for prescription refill function


Analysis of Display ContentAnalysis of Display Content Are different types of data assigned to consistent Are different types of data assigned to consistent

geographic locations on the screen (e.g., photos geographic locations on the screen (e.g., photos always appear in the upper right hand corner)?always appear in the upper right hand corner)?

Can the user customize the screen location for Can the user customize the screen location for content?content?

Is proper on-screen identification assigned to all Is proper on-screen identification assigned to all content? content?

If a large report is to be presented, how should it If a large report is to be presented, how should it be partitioned for ease of understanding?be partitioned for ease of understanding?


• Will mechanisms be available for moving directly to Will mechanisms be available for moving directly to summary information for large collections of data.summary information for large collections of data.

• Will graphical output be scaled to fit within the bounds of the Will graphical output be scaled to fit within the bounds of the display device that is used?display device that is used?

•How will color to be used to enhance understanding?How will color to be used to enhance understanding?

•How will error messages and warning be presented to the How will error messages and warning be presented to the user?user?


Interface Design StepsInterface Design Steps Using information developed during Using information developed during

interface analysis interface analysis define interface objects define interface objects and actions (operations).and actions (operations).

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


Depict each interface stateDepict each interface state as it will actually as it will actually look to the end-user.look to the end-user.

Indicate how the user interprets the state of Indicate how the user interprets the state of the systemthe system from information provided through from information provided through the interface.the interface.


Interface Design PatternsInterface Design Patterns Patterns are available forPatterns are available for

– The complete UIThe complete UI– Page layoutPage layout– Forms and inputForms and input– TablesTables


-Direct data manipulation-Direct data manipulation-Navigation-Navigation-Searching-Searching-Page elements-Page elements-e-Commerce-e-Commerce

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Design IssuesDesign Issues Response timeResponse time Help facilitiesHelp facilities Error handlingError handling Menu and command labelingMenu and command labeling Application accessibilityApplication accessibility InternationalizationInternationalization


Design Evaluation Design Evaluation CycleCyclepreliminary

design

buildprototype #1

interface

evaluationis studied by

designer

designmodifications

are made

buildprototype # n

interface

userevaluate'sinterface

Interface designis complete

Education

Performing user interface design v