HCI Models and Task Analysis

HCI Models

• Goal and Task Hierarchies

  • Hierarchical Model: Involves frameworks such as GOMS (Goals, Operators, Methods, and Selection rules) and HTA (Hierarchical Task Analysis)/TDH (Task Decomposition Hierarchy) that provide structured approaches to user interaction.

  • Focus on mental processing through divide-and-conquer strategies, allowing complex tasks to be broken down into manageable components for ease of understanding and execution.

• Key Concepts

  • Goals: Represent the user's desired outcomes or objectives they aim to achieve through interaction with the system.

  • Operators: Specific actions or operations that a user can perform to achieve their goals. These could be physical actions (like clicking a button) or cognitive actions (like recalling a previous decision).

  • Methods: Sequences of operators that represent the paths users take to accomplish their goals. Multiple methods may exist for achieving the same goal, indicating user flexibility.

  • Selection Rules: Guidelines that help users choose among competing methods, guiding them in selecting the most efficient or preferable approach based on context or prior experience.

• GOMS Analysis

  • GOMS analysis is essential for mastering tasks efficiently, particularly complex tasks such as registration processes in user interfaces.

  • It's particularly helpful when time on task is critical, as it allows for the identification of the most efficient methods and operators, enhancing overall user performance.

  • Analytical model that aids in predicting and evaluating user performance in terms of task completion time and errors, thus optimizing interface design.

• GOMS Example

  • Goal: Close window

  • Methods to achieve this goal include various strategies such as menu-selection (where the user navigates to the menu and selects 'Close') and keyboard shortcuts (like pressing Alt-F4). Each method's efficiency may be evaluated based on user proficiency and context of use.

• Hierarchical Task Analysis (HTA)

  • In HTA, tasks are systematically broken down into ordered subtasks, mimicking the user's thought process and aiding in understanding task complexities.

  • It describes not only user actions but also the relationships between tasks and the underlying knowledge required, creating a comprehensive view of user interaction.

  • Example: Cleaning tasks, such as using a vacuum cleaner, may include subtasks like identifying areas to clean, setting up the vacuum, performing the cleaning, and then putting away the machine. Each subtask has its own goals and methods.

• Generating Task Hierarchies

  • To create task hierarchies, list all potential tasks and strategically group them into higher-level tasks that reflect the primary user objectives.

  • Hierarchical Task Analysis offers a visual mapping of tasks and plans, enabling designers and developers to understand user flows and optimize interfaces accordingly.

• Task Analysis Techniques

  • Task decomposition is crucial for identifying the core components of user interaction and developing efficient strategies for interface improvement.

  • Knowledge-based techniques focus on understanding the user's mental model and how they learn or execute tasks within the system.

  • Entity/object-based analysis looks at the specific objects users interact with and how they facilitate or hinder task completion.

• Planning Models

  • There are various types of plans utilized in interface design, including fixed sequences that define a strict order of actions, optional tasks that offer flexibility in pathways to the same outcome, cycles for repeated actions, and time-sharing models that allow users to manage multiple tasks or processes simultaneously.

  • Understanding these planning models aids in creating interfaces that support user needs more effectively and enhance multitasking capabilities.