Human-Computer Interaction

Human-Computer Interaction

• There are five functions that the user interface provides:
• User may invoke functions provided by the system.
• User may input data to the system.
• System may indicate available functions for the user.
• System may display data to the user.
• System may display status information to the user.

Usability Engineering

• It is aimed at producing practical results using a repeatable process based on scientific principles. Much of the underpinnings of usability engineering is the science of psychology.
• UI Engineering works in parallel with other engineering disciplines: systems engineering, hardware engineering and software engineering.
• It starts with usability requirements analysis.
• The next phase is usability analysis and design.
• Then there is usability testing.
• Usability requirements have to be testable
• Effectiveness
• Efficiency
• Safety
• Utility
• Learnability
• Memorability
• User experience goals
• Satisfying
• Enjoyable
• Fun
• Entertaining
• Helpful
• Motivating
• Aesthetically pleasing
• Supportive of creativity
• Rewarding
• Emotionally fulfilling

Usability Analysis

• Interviewing
• Brainstorming
• Field studies
• Generate operational scenarios

Usability Design

• Process of figuring out how to bridge the gap between how the user wants to use the system and the capabilities provided by the system implementers
• The user’s mental model is based on the user’s goals for using the system.
• The designer’s model is described in terms of mechanisms offered by the system implementation.
• Sometimes this mapping between the user’s model and the designer’s model is accomplished through the use of metaphors
• The usability design process involves describing three aspects of the interaction.
• Activity scenarios – show how the users carry out their goals. We can use UML use cases or activity diagrams for these models.
• Information scenarios – show how information is exchanged between the users and the system. Screen layout prototypes are useful here.
• Interaction scenarios – show the details of how the user and the system interact. Once again, a prototype, either low fidelity or high fidelity, can be used here.
• Several aspects of the user interface that can be prototyped
• Input Controls: These are ways to allow the user to present information to the system.
• Navigational Components provide ways for the user to control the action or the presentation of information.
• Informational Components are mechanisms that enable the system to present information to the user.

User Interface Mechanisms

• Input mechanism
• Keyboard
• graphical user interfaces
• Microphone
• Voice commands
• Video cameras
• Special devices
• Output mechanisms
• Text or graphics
• Auditory output
• Video and animation
• Haptic feedback
• Special devices
• Interacting with systems
• Command line
• Menus
• Form fill-in
• Direct manipulation
• Auditory commands
• Gestures

Error Handling

• Severity
• Useful error messages
• Annoying messages
• Dangerous
• Mistakes are where you have the wrong mental model.
• Slips are where you have the right mental model; you just messed up in execution.
• Handling error
• Do nothing
• Disable
• Issue confirmation prompt
• Provide “undo” capability
• Error Message Guidelines
• Be specific
• Provide constructive guidance
• Be positive
• consistent
• Consider the user’s experience and skill level.
• Consider the culture of the region where the system will be deployed.

Prototyping

• A prototype is a concrete, but partial implementation of a design.
• Its basic purpose is to reduce risk in software development.
• Here are some benefits of prototypes:
• Expose missing system capabilities.
• Expose confusing services.
• Early availability (through evolutionary prototyping).
• Basis for specification of software requirements.
• Support user training.
• Support system testing.
• Low fidelity prototype
• High fidelity prototype
• A useful technique for modeling user interaction is called Screen flows and Layouts.