CS 501: Software Engineering

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CS 501 Software Engineering
Lecture 11 Usability 1
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Course Adminstration
Quiz 2 on Thursday Same format as the first
quiz
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Presentations
Project Presentations First presentation is next
week, Wednesday through Thursday (note change of
date). Meeting room is at 301 College
Avenue. For instructions, read the Assignments
page. Schedule your presentation
now!!!! Available time slots are on the Home
page. Your client must attend the presentation
unless you have special permission.
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Planning for the Presentation
How will you use the time? This is a presentation
to the client, with the Instructor as a
secondary audience. Possible topics Overview
of project and progress against
plan Presentation of assumptions,
decisions Summary of requirements in moderate
detail What has been learned since feasibility
study. Changes in plans Allow 15 minutes for
questions. Expect interruptions. "This is our
understanding of your requirements."
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Planning for the Presentation
Logistics Have a rehearsal, check visual aids
and demonstrations. Then change nothing. Check
out the equipment in the meeting room. What
network will you use (if any). How will you
connect a computer (if you do)? What about
firewalls? Will one person act as chair and call
on other members of the team? Never interrupt
your colleagues. Not everybody is a great
presenter, but everybody can be well-prepared.
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Design
Your understand the requirements, now to design
the system.
Feasibility and Planning
Requirements
Design
Operation and Maintenance
Implementation
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What is Design?
Design is conscious Design keeps human concerns
in the center Design is a dialog with
materials Design is creative Design is
communication Design has social
consequences Design is a social activity Terry
Winograd Bringing Design to Software, 1996
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Software Design
The design phase is the most creative part of
software development. The design must Meet
the requirements Satisfy the users Provide
flexibility for changing requirements Be
suitable for implementation with available
resources Be testable and maintainable Fit
within the style of the organization(s)
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Reading
Reading  Mitchell Kapor, A Software Design
Manifesto. Dr. Dobbs Journal, 1991.
http//hci.stanford.edu/bds/1-kapor.html "Software
design is not the same as user interface
design." "Architects, not construction engineers,
are the professionals who have overall
responsibility for creating buildings. ... in the
actual process of designing and implementing the
building, the engineers take direction from the
architects."
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Lectures on Design
Lectures Topic 11-12 Usability 13-14 System
Architecture 15-16 Object Oriented
Design 17-18 Tools and Techniques
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Design for Usability
Usability of a computer system is a combination
of factors User interface design
Functionality Performance Help systems and
documentation Freedom from errors Anything
else?
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User Interface Design
The user interface design is the appearance on
the screen and the actual manipulation by the
user (look and feel) Fonts, colors, logos,
key board controls, menus, buttons Mouse
control or keyboard control? Conventions
(e.g., "back", "help")
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Same Functions, Different Interface
The user interface design is different from the
functionality provided. Example 1 Microsoft
Word on Windows and Macintosh Different user
interfaces for the same functionality. Example 2
The desk top metaphor Mouse -- 1 button
(Macintosh), 2 button (Windows) or 3
button (Unix) Close button -- left of window
(Macintosh) right of window
(Windows)
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User Interface Design
Examples of change 1990 to 2004
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1990
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1995
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2003
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1995
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2003
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1995
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2003
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1995
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2003
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User Interface Design Requirements and
Refinement

• It is very difficult to specify and comprehend an
  interactive
• interface in a textual documents.
• Requirement documents benefit from sketches,
  comparison with existing systems, etc.
• Design documents should definitely include
  graphical elements and often benefit from a
  mock-up or other form of prototype.
• Implementation plans should include evaluation of
  user factors and time to make changes.
• USER INTERFACES MUST BE TESTED WITH USERS

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The Design/Evaluate Loop
Design
Analyze requirements
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Build
Evaluate
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Mock-up Example
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Methods for Specifying Usability Requirements and
Evaluation of Usability
Initial Mock-up Prototype Production Client's
opinions ? ? ? Competitive
analysis ? Expert opinion ? ?
Focus groups ? ? Observing users
? ? ? Measurements ? ?
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Focus Group
A focus group is a group interview Interviewer
Potential users Typically 5 to 12 Similar
characteristics (e.g., same viewpoint) Structure
d set of questions May show mock-ups Group
discussions Repeated with contrasting user
groups
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Usability Laboratory
Monitor users while they use system (or a
prototype)
Evaluators User
one-way mirror
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Usability Laboratory
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Usability Laboratory
Observing techniques Human observer Video
camera Tape recording Study techniques Human
protocol (user talks aloud while using
system) User carries out specified list of
tasks Software designer presents story board
(mock-up) to user
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Eye Tracking
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Eye Tracking
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Measurement
Basic concept log events in the users'
interactions with a system Examples from a Web
system Clicks (when, where on screen,
etc.) Navigation (from page to
page) Keystrokes (e.g., input typed on
keyboard) Use of help system Errors May be
used for statistical analysis or for detailed
tracking of individual user.
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Principles of Interface Design
Interface design is partly an art there are
general principles Consistency -- in
appearance, controls, and function. Feedback
-- what is the computer system is doing?
why does the user see certain results?
Users should be able to interrupt or reverse
actions Error handling should be simple and
easy to comprehend Skilled users offered
shortcuts beginners have simple, well-defined
options The user should feel in control
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Style of User InterfacesCommand Line Interfaces
User interacts with computer by typing commands
Allows complex instructions to be given to
computer Facilitates formal methods of
specification implementation Skilled users
can input commands quickly Requires
learning or training Can be adapted for
people with disabilities Can be
multi-lingual Suitable for scripting /
non-human clients
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Style of User InterfacesDirect Interaction
User interacts with computer by manipulating
objects on screen Can be intuitive and easy
to learn Users get immediate feedback
Not suitable for some complex interactions
Does not require typing skills
Straightforward for casual users, slow for
skilled users Icons can be
language-independent Difficult to build
scripts Only suitable for human users
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Design for Direct Manipulation
metaphors and mental models Conceptual models,
metaphors, icons, but there may not be an
intuitive model navigation rules How to move
among data functions, activities and roles in a
large space conventions Familiar aspects that do
not need extra training. gt scroll bars,
buttons, help systems, sliders gt good for
users, good for designers look characteristics
of the appearance that convey information feel
interaction techniques that provide an appealing
experience
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Design for Direct ManipulationMenus
Easy for users to learn and use Certain
categories of error are avoided Enables
context-sensitive help Major difficulty is
structure of large choices Scrolling menus
(e.g., states of USA) Hierarchical
Associated control panels Menus plus command
line Users prefer broad and shallow to deep menu
systems
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2003
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2004
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Help System Design
Help system design is difficult! Must
prototype with mixed users Categories of
help gt Overview and general information gt
Specific or context information gt Tutorials
(general) gt Cook books and wizards gt
Emergency ("I am in trouble ...") Must have
many routes to same information Never blame the
user!