CS CS 5150 Software Engineering Lecture 11 Usability 1

CS 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 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 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 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 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 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 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 change the requirements as the result of testing.

CS Tools for Usability Requirements and Evaluation Initial Mock-upPrototypeProduction Client's opinions    Competitive analysis  Expert opinion   Focus groups   Observing users    Measurements  

CS Tools for Usability Requirements: Mock-up

CS 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 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

CS Usability Requirements: Device-aware User Interfaces Examples: desk-top computer, fast network connection laptop computer, intermittent connectivity iPod, synchronization smart telephone digital camera, camcorder Device-aware user interfaces: => performance of device => limited form factor (display, keyboard) => connectivity

CS Usability: Non-Functional Requirements Performance, Reliability, Scalability, Security… Example: Response time 0.1 sec – the user feels that the system is reacting instantaneously 1 sec – the user will notice the delay, but his/her flow of thought stays uninterrupted 10 sec – the limit for keeping the user's attention focused on the dialogue

CS Design from a System Viewpoint interface design functional design data and metadata computer systems and networks mental model

CS 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 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 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 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 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 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 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 Command Line Interfaces and Text-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 Design: Command Line Interfaces

CS 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 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 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 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 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 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 Separation of Presentation from Content Information to be displayed Presentation software Display Presentation software Display PDF Acrobat html Firefox