Seii unit5 ui_design

2
Interface Design
Easy to use?Easy to use?
Easy to understand?Easy to understand?
Easy to learn?Easy to learn?

3
Interface Design
lack of consistencylack of consistency
too much memorizationtoo much memorization
no guidance / helpno guidance / help
no context sensitivityno context sensitivity
poor responsepoor response
unfriendlyunfriendly
Typical Design ErrorsTypical Design Errors

4
Golden Rules
 Place the user in control
 Reduce the user’s memory load
 Make the interface consistent

5
Place the User in Control
Define interaction modes in a way that does notDefine interaction modes in a way that does not
force a user into unnecessary or undesired actions.force a user into unnecessary or undesired actions.
Provide for flexible interaction.Provide for flexible interaction.
Allow user interaction to be interruptible andAllow user interaction to be interruptible and
undoable.undoable.
Streamline interaction as skill levels advance andStreamline interaction as skill levels advance and
allow the interaction to be customized.allow the interaction to be customized.
Hide technical internals from the casual user.Hide technical internals from the casual user.
Design for direct interaction with objects that appearDesign for direct interaction with objects that appear
on the screen.on the screen.

6
Reduce the User’s Memory Load
Reduce 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 based on aThe visual layout of the interface should be based on a
real world metaphor.real world metaphor.
Disclose information in a progressive fashion.Disclose information in a progressive fashion.

7
Make the Interface Consistent
Allow the user to put the current task into aAllow the user to put the current task into a
meaningful context.meaningful context.
Maintain consistency across a family ofMaintain consistency across a family of
applications.applications.
If past interactive models have created userIf past interactive models have created user
expectations, do not make changes unless there isexpectations, do not make changes unless there is
a compelling reason to do so.a compelling reason to do so.

These slides are designed to accompany Software Engineering: A Practitioner’s Approach, 7/e
(McGraw-Hill, 2009) Slides copyright 2009 by Roger Pressman. 8
User Interface Design Models
 User model — a profile of all end users of
the system
 Design model — a design realization of the
user model
 Mental model (system perception) — the
user’s mental image of what the interface is
 Implementation model — the interface “look
and feel” coupled with supporting information
that describe interface syntax and semantics

User Interface Design Process

Interface Analysis
 Interface analysis means understanding
 (1) the people (end-users) who will interact with the
system through the interface;
 (2) the tasks that end-users must perform to do their
work,
 (3) the content that is presented as part of the
interface
 (4) the environment in which these tasks will be
conducted.

User Analysis
 Are users trained professionals, technician, clerical, or manufacturing workers?
 What level of formal education does the average user have?
 Are the users capable of learning from written materials or have they
expressed a desire for classroom training?
 Are users expert typists or keyboard phobic?
 What is the age range of the user community?
 Will the users be represented predominately by one gender?
 How are users compensated for the work they perform?
 Do users work normal office hours or do they work until the job is done?
 Is the software to be an integral part of the work users do or will it be used only
occasionally?
 What is the primary spoken language among users?
 What are the consequences if a user makes a mistake using the system?
 Are users experts in the subject matter that is addressed by the system?
 Do users want to know about the technology the sits behind the interface?

Task Analysis and Modeling
 Answers the following questions …
 What work will the user perform in specific circumstances?
 What tasks and subtasks will be performed as the user does
the work?
 What specific problem domain objects will the user manipulate
as work is performed?
 What is the sequence of work tasks—the workflow?
 What is the hierarchy of tasks?
 Use-cases define basic interaction
 Task elaboration refines interactive tasks
 Object elaboration identifies interface objects (classes)
 Workflow analysis defines how a work process is
completed when several people (and roles) are involved

Analysis of Display Content
 Are different types of data assigned to consistent geographic
locations on the screen (e.g., photos always appear in the
upper right hand corner)?
 Can the user customize the screen location for content?
 Is proper on-screen identification assigned to all content?
 If a large report is to be presented, how should it be partitioned
for ease of understanding?
 Will mechanisms be available for moving directly to summary
information for large collections of data.
 Will graphical output be scaled to fit within the bounds of the
display device that is used?
 How will color to be used to enhance understanding?
 How will error messages and warning be presented to the
user?

Interface Design Steps
 Using information developed during interface
analysis, define interface objects and actions
(operations).
 Define events (user actions) that will cause the
state of the user interface to change. Model
this behavior.
 Depict each interface state as it will actually
look to the end-user.
 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

WebApp Interface Design
 Where am I? The interface should
 provide an indication of the WebApp that has been accessed
 inform the user of her location in the content hierarchy.
 What can I do now? The interface should always help the user
understand his current options
 what functions are available?
 what links are live?
 what content is relevant?
 Where have I been, where am I going? The interface must
facilitate navigation.
 Provide a “map” (implemented in a way that is easy to understand)
of where the user has been and what paths may be taken to move
elsewhere within the WebApp.

Effective WebApp Interfaces
 Bruce Tognozzi [TOG01] suggests…
 Effective interfaces are visually apparent and
forgiving, instilling in their users a sense of control.
Users quickly see the breadth of their options, grasp
how to achieve their goals, and do their work.
 Effective interfaces do not concern the user with the
inner workings of the system. Work is carefully and
continuously saved, with full option for the user to
undo any activity at any time.
 Effective applications and services perform a
maximum of work, while requiring a minimum of
information from users.


The complete UI
Page layout
Forms and input
Tables
Direct data manipulation
Navigation
Searching
Page elements
e-Commerce
Interface Design Patterns/Tools

Interface Design Principles-I
 Anticipation—A WebApp should be designed so that it
anticipates the use’s next move.
 Communication—The interface should communicate the status
of any activity initiated by the user
 Consistency—The use of navigation controls, menus, icons,
and aesthetics (e.g., color, shape, layout)
 Controlled autonomy—The interface should facilitate user
movement throughout the WebApp, but it should do so in a
manner that enforces navigation conventions that have been
established for the application.
 Efficiency—The design of the WebApp and its interface should
optimize the user’s work efficiency, not the efficiency of the
Web engineer who designs and builds it or the client-server
environment that executes it.

Interface Design Principles-II
 Focus—The WebApp interface (and the content it presents) should
stay focused on the user task(s) at hand.
 Fitt’s Law—“The time to acquire a target is a function of the distance to
and size of the target.”
 Human interface objects—A vast library of reusable human interface
objects has been developed for WebApps.
 Latency reduction—The WebApp should use multi-tasking in a way
that lets the user proceed with work as if the operation has been
completed.
 Learnability— A WebApp interface should be designed to minimize
learning time, and once learned, to minimize relearning required when
the WebApp is revisited.

Interface Design Principles-III
 Maintain work product integrity—A work product (e.g., a form
completed by the user, a user specified list) must be automatically
saved so that it will not be lost if an error occurs.
 Readability—All information presented through the interface should be
readable by young and old.
 Track state—When appropriate, the state of the user interaction should
be tracked and stored so that a user can logoff and return later to pick
up where she left off.
 Visible navigation—A well-designed WebApp interface provides “the
illusion that users are in the same place, with the work brought to
them.”

Interface Design Workflow-I
 Review information contained in the analysis model
and refine as required.
 Develop a rough sketch of the WebApp interface
layout.
 Map user objectives into specific interface actions.
 Define a set of user tasks that are associated with each
action.
 Storyboard screen images for each interface action.
 Refine interface layout and storyboards using input
from aesthetic design.

Mapping User Objectives
objective #1
objective #2
objective #3
objective #4
objective #5
objective #n
List of user objectives
Home page text copy
graphic
graphic, logo, and companyname
Navigation
menu
Menu bar
major functions

Interface Design Workflow-II
 Identify user interface objects that are
required to implement the interface.
 Develop a procedural representation of the
user’s interaction with the interface.
 Develop a behavioral representation of the
interface.
 Describe the interface layout for each state.
 Refine and review the interface design
model.

Visual Design
 Don’t be afraid of white space.
 Emphasize content.
 Organize layout elements from top-left to
bottom right.
 Group navigation, content, and function
geographically within the page.
 Don’t extend your real estate with the scrolling
bar.
 Consider resolution and browser window size
when designing layout.

Design Evaluation Cycle
preliminary
design
build
prototype #1
interface
evaluation
is studied by
designer
design
modifications
are made
build
prototype #n
interface
user
evaluate's
interface
Interface design
is complete

Seii unit5 ui_design

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