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Interface Design

Interface Design. Instructor: Dr. Jerry Gao. Interface Design. - Interface design - Internal and external interfaces - User interfaces - User interface design - User interface design principles - User-system interaction - Interface models - Menu systems - Command-line interface

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Interface Design

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  1. Interface Design Instructor: Dr. Jerry Gao

  2. Interface Design - Interface design - Internal and external interfaces - User interfaces - User interface design - User interface design principles - User-system interaction - Interface models - Menu systems - Command-line interface - Information representation - Information display - Data input - User guidance - error messages, help system design, user documentation - Interface evaluation Jerry Gao, Ph.D. Jan. 1999

  3. Interface Design Interface design focuses on three areas: a) the design of interfaces between software modules b) the design of interfaces between the software and other non-human procedures and consumers of information c)the design of the interface between a human and the computer Internal and external interface design: - The design of internal program interfaces, ---> called intermodular interface design -----> the interfaces between internal functional processes in DFDs. That is, they can be mapped to the transactions between processes. External interface design ----> - Checking the external entities in DFDs. - Design of the interfaces between external entities and internal processes. ->Have something to do with external data and external control

  4. User Interface Design Principles User familiarity: The interface should use terms and concepts which are drawn from the experience of the anticipated class of user. Consistency: The interface should be consistent in that comparable operation should be activated in the same way. Minimal surprise: Users should never be surprised by the behavior of a system Recoverability: The interface should include mechanisms to allow users to recover from their errors. - confirmation of destructive actions - the provision of an undo facility User guidance: The interface should incorporate some form of context-sensitive user guidance and assistance.

  5. Interface Design Guidelines General Interaction: - Be consistent - Offer meaningful feedback - Ask for verification of any nontrivial destructive action - Permit easy reversal of most actions - Reduce the amount of information that must be memorized between actions - Seek efficiency in dialog, motion, and thought - Forgive mistakes - Categorize activities by function and organize screen geography accordingly - Provide help facilities that are context sensitive - Use simple action verbs or short verb phrases to name commands

  6. User System Interactions Interaction models: A) Direct manipulation: --> a direct manipulation interface presents users with a model of their information space. They interact with this information through direct actions, such as replacing information, moving information, and so on. Example: screen editors or work processors B) Menu systems: In a menu interface, users select one of a no. of possibilities to issue a command to the machine. They may use a mouse, such as pointing, moving, selecting… C) Command-line interfaces: Command interfaces require the user to type a text command to the system. The command may be a query, a request for some service or it may call up a sequence of other commands.

  7. User System Interactions Direct manipulation: Advantages: - Users feel in control of the computer and are not intimidated by it. - User learning time is relatively short. - User get immediate feedback on their actions. Mistakes can often be detected and corrected quickly. Problems: - How can an appropriate information model and metaphors be derived? - Given that users have a large information space, how can they navigate around that space and always aware of their current position? - Interfaces usually are complicated. One simple approach is: a form-based interface:

  8. User System Interactions Pull-down menu Menu systems: (a) pull-down menus: (predictable, but need more screen space) - display the menu title. User can select commands through this menu. (b) pop-up menus: (flexible, tailorable, may cause user surprise) - They are associated with entities (such as a field). Selecting the entity then clicking a mouse button --> cause the menu to appear. Advantages: - Users do not need to know the command names. - Typing efforts is minimal. - Some user errors can be avoid. - Context-dependent help can be provided. Problems: - Take care the structure of large menus. Solutions: a) scrolling menus, b) hierarchical menus c) walking menus, d) associated control panels Pop-up menu Walking menu

  9. User System Interactions Command-line interfaces: Advantages: - Implementation is easy and simple due to the language processing. - It can support very complex systems with a lot of commands. - User interface needs a little effort. - Typing efforts is minimal. - Some user errors can be avoid. - Context-dependent help can be provided. Problems: - Users must learn and remember all commands. - Hard to learn the system and not easy for operations. - Users inevitably make errors. Notice: command-line interfaces and menu-based interfaces are not mutually exclusive.

  10. User System Interactions Interface models --> GUI interfaces with well-predefined GUI formats and styles. (X windows and Motif, Micro software Windows, ….) It includes various elements: - buttons, switches, menus, indicators, displays, sliders. - windows, panels, dialog boxes,… - icons, tool bars, …. Advantages: - GUI is very attractive due to its nice GUI styles/ formats. - Very easy to learn and to operate. Problems: - GUI styles and formats should be standardized. - GUI design is complicated. - Implementation is complex and expansive. It usually is the combination of: menu-systems, command-line interfaces, direct manipulation, ...

  11. Information Representation There are a number of ways to represent information in a user interface: - Text, data, tables - 2-D (or 3-D) picture, diagrams - Multi-media (image, animation, sound, video, …) The representation can be affected by the following factors: - color, size, motion, resolution, … - screen (or window) layout, operational sequence - GUI hierarchical structure Types of representation information: - Input data (typed data, selective data, default data) - Output data, tables, reports, diagrams, or pictures - Error messages and waning messages GUI elements: - windows (screens), panels - menus (pull-down, pop-up, nested-menu) - buttons, tool bars, icons - check list, selection list, choice box, radio box - text field, text area, label,

  12. Information Representation - Display Display Guidelines: - Display the relevant information to the current context. - Don’t bury the user with data, use a presentation format. - Use consistent labels, standard abbreviations, and predictable colors. - Allow the user to maintain visual context. - Produce meaningful error messages. - Use upper and lower case, indention, and text grouping to help understanding. - Use windows to compartmentalize different types of information. - Use ‘analog’ displays to represent information that is more easily assimilated with this form of representation. - Consider the available geography of the display screen and use it efficiently.

  13. Information Representation - Display The filename you have chosen has been used. Please choose another name. XXXXXX ok cancel 1 Dial with needle Pie chart 4 2 3 0 10 20 Horizontal bar

  14. Information Representation - Input Input Data Guidelines: - Minimize the number of input actions required of the user. (selective data, default data…) - Maintain consistency between information display and data input. (color, size, and placement) - Interaction should be flexible but also tuned to the user’s preferred mode of input.. (for example, keyboard input, or mouse input) - Deactivate commands that are inappropriate in the context of current actions. - Let the user control the interactive flow. - Provide help to assist with all input actions. - Eliminate “mickey mouse” input.. (default values)

  15. User Guidance Three types of user guidance : (Figure 17.12, 17.14, 17.15, 17.16 [2]) - the messages produced by the system in response to user actions - the on-line help system - the documentation provided with the system Integrated help and message system Application Help interface Error message system Message presentation system Help frames Error message texts

  16. User Documentation System evaluators System administrators Novice users Experienced users System administrators Functional description Installation document Introductory manual Reference manual Administrator’s guide Description of services How to install the system Getting started Facility description Operation and maintenance

  17. User Interface Evaluation Evaluation Guidelines: - Questionnaires which collect information from uses about the interface: - Learnability: How long does it take a new user to familiar with the system operations? - Speed of operation: How well does the system response match the user’s work practice? - Robustness: How tolerant is the system of user errors? - Recoverability: How good is the system at recovering from user errors? - Adaptability: How closely is the system tied to a single model of work? - Observation of users at work with the system and “thinking aloud” about how they are trying to use the system to accomplish some task; - Video “snapshots” of typical system use; - Include software to identify most-used facilities and common user errors

  18. User Interface Evaluation Preliminary design Build prototype #1 Interface The evaluation cycle for user interface design Build prototype #n interface Design modifications are made User evaluates interface Interface Design is completed Evaluation is studied by designer

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