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CS 5150 1
CS 5150 Software Engineering
Lecture 11
Usability 1
CS 5150 2
Course Administration
Test 2 this evening
Same format as the first test
Weekly reports
Alex Fix will read the reports and send you any messages about them.
Be sure that the report includes a brief summary of what was planned for last week, what was achieved, and what is planned for this week.
CS 5150 3
Planning for the Presentation
How will you use the time?
This is a presentation to the client, with the instructor and teaching assistant 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..."
CS 5150 4
Planning for the Presentation
Not everybody is a great presenter, but everybody can be well-prepared.
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?
CS 5150 5
During the Presentation
• The presenter should stand. Other people should sit.
• Appoint a team member to take notes.
• The first presenter should introduce everybody.
• When asked a question:
-> If the presenter knows the answer, answer it.-> Or the presenter may ask another team member to answer.-> Otherwise make a note and reply later.
• Never interrupt your colleagues. If you have information to add, raise you hand and the presenter can decide whether to call on you.
CS 5150 6
The Importance of User Interface Design
Good support for users is more than a cosmetic flourish
• Elegant design, appropriate functionality, & responsive system: => a measurable difference to their effectiveness
• A system that is hard to use: => users may fail to find important results, or mis-interpret what they do find=> user may give up in disgust
A computer system is only as good as the interface it provides to its users
CS 5150 7
Usability: The Analyze/Design/Evaluate Loop
Evaluate
?Design
Build
Analyze requirements
The Information Science program and Communication Department offer a series of courses in Human Computer Interaction.
User testing
CS 5150 8
Requirements for User Interfaces
It is almost impossible to specify an interactive interface in a textual document
• Requirement documents benefit from sketches, comparison with existing systems, etc.
• Design documents should definitely include graphical elements and benefit from a mock-up or other form of prototype.
• Schedules should include user testing and time to make changes.
User interfaces must be tested with users. Expect to changethe requirements as the result of testing.
CS 5150 9
Tools for Usability Requirements and Evaluation
Initial Mock-up Prototype Production
Client's opinions
Competitive analysis
Expert opinion
Focus groups
Observing users
Measurements
CS 5150 10
Tools for Usability Requirements:
Mock-up
CS 5150 11
Tools for Usability Requirements: Focus Group
A focus group is a group interview
• Interviewer
• Potential users
Typically 5 to 12
Similar characteristics (e.g., same viewpoint)
• Structured set of questions
May show mock-ups
Group discussions
• Repeated with contrasting user groups
CS 5150 12
Usability:Accessibility Requirements
Requirements about accessibility (e.g., support for users with disabilities) are most likely to arise in the user interface.
You may have a legal requirement to support people with disabilities.
Example of requirements specification:
The system must comply with Section 508 of the US Rehabilitation Act. See http://www.section508.gov/
CS 5150 13
Usability Requirements: Device-aware User Interfaces
Examples:
desk-top computer, fast network connectionlaptop computer, intermittent connectivityiPod, synchronizationsmart telephonedigital camera, camcorder
Device-aware user interfaces:
=> performance of device=> limited form factor (display, keyboard)=> connectivity
CS 5150 14
Usability: Non-Functional Requirements
Performance, Reliability, Scalability, Security…
Example: Response time0.1 sec – the user feels that the system is reacting instantaneously1 sec – the user will notice the delay, but his/her flow of thought stays uninterrupted10 sec – the limit for keeping the user's attention focused on the dialogue
CS 5150 15
Design from a System Viewpoint
interface design
functional design
data and metadata
computer systems and networks
mentalmodel
CS 5150 16
Mental Model
What a person thinks is true about a system, not necessarily what is actually true
• Similar in structure to the system that is represented
• Allows a person to predict the results of his actions
• Simpler than the represented system. A mental model includes only enough information to allow accurate predictions (i.e. no data structures)
Also called conceptual model
CS 5150 17
Examples of Mental Model
The mental (conceptual) model is the user's internal model of what the system provides:
• The desk top metaphor -- files and folders
• The Web model -- one vast collection of pages with hyperlinks
CS 5150 18
Interface Design
The interface design is the appearance on the screen and the actual manipulation by the user
• Fonts, colors, logos, key board controls, menus, buttons
• Mouse control or keyboard control
• Conventions (e.g., "back", "help")
Examples:
• Screen space utilization in Acrobat.
• Number of snippets per page in Web search.
CS 5150 19
Principles of Interface Design
Interface design is partly an art, but there are general principles:
• Consistency -- in appearance, controls, and function.
• Feedback -- what is the computer system 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 should be offered shortcuts; beginners should have simple, well-defined options
The user should feel in control
CS 5150 20
Functional Design
The functional design, determines the functions that are offered to the user
• Selection of parts of an object
• Searching a list or sorting the results
• Help information
• Manipulation of objects on a screen
• Pan or zoom
There may be many user interface choices for the same function, e.g., Macintosh v. Windows desktop
CS 5150 21
Data and Metadata
Structural data and metadata stored by the computer system enable the functions and the interface
• Effectiveness of searching depends on the type and quality of data that is indexed (free-text, controlled vocabulary, etc.)
• The desktop metaphor has the concept of associating a file with an application. This requires a file type to be stored with each file:
-- extension to filename (Windows and Unix) -- resource fork (Macintosh)
CS 5150 22
Computer Systems and Networks
The performance, reliability and predictability of computer systems and networks is crucial to usability
Examples
• Instantaneous response time for mouse tracking and echo of key stroke
• Pipelined algorithm for the Mercury page turner
• Quality of Service for real time information
CS 5150 23
Command Line Interfaces andText-only Menus
Command line interfaces and text-only menus had become almost entirely replaced by graphical interfaces, but are returning:
• Devices with small form factor or other special features, e.g. cell phone, PDA, etc.
• Interfaces for simple tasks with general users, e.g. automated bank teller (ATM)
CS 5150 24
Design: Command Line Interfaces
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CS 5150 25
Design: Command 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
• Unless very simple, requires learning or training
• Can be adapted for people with disabilities
• Can be multi-lingual
• Suitable for scripting / non-human clients
CS 5150 26
Design:Graphical Interfaces and Direct 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, may be slow for skilled users
• Icons can be language-independent
• Difficult to build scripts
• Only suitable for human users
CS 5150 27
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.
=> scroll bars, buttons, help systems, sliders
=> good for users, good for designers
look: characteristics of the appearance that convey information
feel: interaction techniques that provide an appealing experience
CS 5150 28
Design for Direct Manipulation: Menus
• 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
CS 5150 29
Help System Design
Help system design is difficult
• Must prototype with mixed users
• Categories of help:
=> Overview and general information=> Specific or context information=> Tutorials (general)=> Cook books and wizards=> Emergency ("I am in trouble ...")
• Must have many routes to same information
Never blame the user!
CS 5150 30
Information Presentation
Simple is often better than fancy
• Text
precise, unambiguous
fast to compute and transmit
• Graphical interface
simple to comprehend / learn
uses of color
variations show different cases
CS 5150 31
Separation of Presentation from Content
Information to be displayed
Presentation software Display
Presentation software
Display
Acrobat
html
Firefox
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