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Chapter 12 Designing Interfaces and Dialogues
Objectives:
Explain the process of interface and dialogue design.
Contrast and apply methods for interacting with a system.
List and describe various input devices and factors affecting their usability.
Describe guidelines for designing interface layout, data entry field structure, feedback, and system help.
Design graphical user interfaces.
Interface/Dialogue Design
Layout (of widgets, text, and table data) Structuring data entry (tab order) Controlling data input (validation and
format controls) Feedback (prompting, status, warning,
and error messages) Dialogue sequencing
Deliverables and Outcomes
A typical interface/dialogue design specification:
Similar to form design, but includes dialogue sequence specifications
Interface Methods
Interface: the method by which a user interacts with the information system
Common interaction methods
•Command line
•Menu
•Form
•Object-based
•Natural language
Command Line Interaction
Users enter explicit statements into a system to invoke operations
Example from MS DOS:
•COPY C:PAPER.DOC A:PAPER.DOC
•This copies a file from the C: drive to the A: drive
Includes keyboard shortcuts and function keys Experienced users and for rapid interaction with
a system User interface standards
Menu Interaction
A list of system options is provided and specific command is invoked by user selection of a menu option
Two common menu types:
•Pop-up: menu placed near current cursor position
• List of commands or possible values
•Drop-down: access point to menu placed at top line of display, menu drops down when access point clicked
Guidelines for Menu Design
Wording: meaningful titles, clear command verbs, mixed upper/lower case
•Quit prior menu or exit program? Organization: consistent organizing principle
•Related options grouped together
•Same option should have the same wording Length: all choices fit within screen length
•Use submenus to break up exceedingly long menus
Guidelines for Menu Design
Selection: consistent, clear and easy selection methods
•How to select and the consequences of each option – will another menu appear?
Highlighting: only for selected options (check mark) or unavailable options (dimmed text)
Use menu building tools
Poor Menu Design
Good Menu Design
Form Interaction
Allows users to fill in the blanks when working with a system
Measures of an effective design:
•Self-explanatory title and field headings
•Fields organized into logical groupings
•Distinctive boundaries
•Default values
•Displays appropriate field lengths
•Minimizes the need to scroll windows
Object Interaction
Symbols are used to represent commands or functions.
Icons:
•Graphic symbols that look like the processing option they are meant to represent
•Use little screen space
•Can be easily understood by users
Natural Language Interaction
Inputs to and outputs from system are in a conventional speaking language like English
Based on research in artificial intelligence Current implementations are tedious and
difficult to work with, not as viable as other interaction methods
Hardware Options for System Interaction
Keyboard Mouse Joystick Trackball
Make selection during logical design!!!
Touch Screen Light Pen Graphics Tablet Voice
Different interfaces require different devices
Types of Interaction Device Usability Problems
Visual Blocking: extent to which device blocks display when using
User Fatigue: potential for fatigue over long use Movement Scaling: extent to which device
movement translates to equivalent screen movement
Durability: lack of durability or need for maintenance (e.g., cleaning) over extended use
Types of Interaction Device Usability Problems
Adequate feedback: extent to which device provides adequate feedback for each operation
Speed: cursor movement speed Pointing accuracy: ability to precisely direct
cursor
Usability Problems with Hardware Devices
Visual Blocking• touch screen, light pen
User Fatigue• touch screen, light pen
Movement Scaling• keyboard, mouse,
joystick, trackball, graphics tablet, voice
Durability• trackball, touch screen
Adequate Feedback• keyboard, mouse,
joystick, trackball, graphics tablet, voice
Speed• keyboard
Pointing Accuracy• joystick, touch screen,
light pen, voice
Designing Interfaces
Use standard formats similar to paper-based forms and reports
Consistently format across applications Left-to-right, top-to-bottom screen navigation Areas of screen not used for data entry should
be inaccessible to users
Designing Interfaces
Flexibility and consistency:• Free movement between fields, forward and
backward• No permanent data storage until the user requests • Each key and command assigned to one function
and this should be consistent across the entire system and across systems, if possible
Data entry screen functional capabilities (Table 12-5):• Cursor control forward, backward, first, last field,
etc.• Delete the character to the left of the cursor, under
the cursor, etc.
Structuring Data Entry
Entry Never require data that are already online or that can be computed
Defaults Always provide default values when appropriate
Units Make clear the type of data units requested for entry
Replacement Use character replacement when appropriate – look up value in table or automatically fill in
Captioning Always place a caption adjacent to fields
Format Provide formatting examples – show embedded symbols
Justify Automatically justify data entries
Help Provide context-sensitive help when appropriate
Entering Text
Controlling Data Input
Objective: reduce data entry errors Common sources data entry errors in a field:
•Appending: adding additional characters
•Truncating: losing characters
•Transcripting: entering invalid data
•Transposing: reversing sequence of characters
Types of Validation Tests
Class or Composition Combinations Expected Values – match with existing Missing Data Range Reasonableness Self-checking Digits Size - # of characters Values – standard (state codes)
Feedback Messages
Status information: keep user informed of what’s going on, helpful when user has to wait for response
Prompting cues: tell user when input is needed, and how to provide the input• Should be specific
Warning or Error: inform user that something is wrong, either with data entry or system operation:• Specific, no jargon, don’t scold user
• Same format, placement
Providing Help
Place yourself in user’s place when designing help Guidelines:
• Simplicity• Help messages should be short and to the point• Use complete sentences and words that enable
understanding• Organize
• Information in help messages should be easily absorbed by users – bulleted or ordered list
• Show• It is useful to explicitly show users how to perform
an operation Use tools to design system help
• HTML help environment – text editor to construct help pages that can be easily linked
What is a Dialogue?
A sequence of interactions between the system and a user
Dialogue design involves:
•Designing a dialogue sequence
•Building a prototype
•Assessing usability
Guidelines for Dialogue Design
Consistency Shortcuts and
Sequence (natural) Feedback for every
user action (confirm add, delete)
Closure – there are no more screens
Error Handling – detect, report, make suggestions
Reversal – undo a delete
Control Ease of use
Dialogue Diagramming
A formal method for designing and representing human-computer dialogues using box and line diagrams
Dialogue diagrams depict the sequence, conditional branching, and repetition of dialogues
Designing Interfaces and Dialogues in Graphical Environments
Become an expert user of the GUI environment.• Understand how other applications have been
designed. • Understand standards.
Gain an understanding of the available resources and how they can be used.• Become familiar with standards for menus and
forms• File menu is always first• Help is always last• Right arrow shows that item leads to a
submenu
GUI Window Properties That Can Be Turned On or Off
Modality: require user to finish action before proceeding
Resizable: allow user to change size of window Movable: allow user to reposition window Maximize: allow user to make window take
entire screen Minimize: allow user to completely hide window System menu: allow window to have access to
system level functions
GUI Dialogue Design Issues
Goal is to establish the sequence of displays that users will encounter when working with system.
Ability of some GUI environments to jump from application to application or screen to screen makes sequencing a challenge.
One approach is to make users always resolve requests for information before proceeding, although this doesn’t take advantage the GUI’s task-switching capability.
Dialogue diagramming helps analysts better manage the complexity of designing graphical interfaces.