Content - 3.4.2
Introduction & Overview
Read summaries of the section's main ideas at different levels of detail.
Quick Overview
Standard
This section provides an in-depth look at the GOMS model, a hierarchical cognitive framework. It meticulously defines Goals (user objectives), Operators (atomic actions), Methods (sequences of operators and sub-goals), and Selection Rules (criteria for choosing among methods), illustrating how these components collectively model an expert user's structured approach to task execution.
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Detailed Summary
Detailed Summary of the Comprehensive Components of the GOMS Model
The GOMS (Goals, Operators, Methods, Selection Rules) model is a sophisticated, hierarchical cognitive model that builds upon simpler models like KLM. It explicitly represents the knowledge an expert user possesses to effectively interact with a system and accomplish tasks. This section meticulously defines each of its four core components:
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Goals (G):
- Definition: Goals are the high-level objectives or intentions that drive user interaction. They represent what the user wants to achieve.
- Nature: They are declarative statements of intent and can be broken down into nested sub-goals, forming a hierarchical structure.
- Examples:
GOAL: Edit-Document,GOAL: Send-Email,GOAL: Print-Document.
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Operators (O):
- Definition: Operators are the basic, atomic (unanalyzable) perceptual, cognitive, and motor actions performed by a user, or actions performed by the system, to work towards a goal.
- Categorization: They can be internal (cognitive/perceptual, e.g.,
Recall-Command,Read-Text) or external (motor, e.g.,Type-Character,Click-Mouse). System responses (System-Response-Time) are also included. - Relationship to KLM: KLM's operators (K, P, H, M, R) are a subset of the operators used in a full GOMS model, which allows for a richer and more context-specific set.
- Examples:
TypeString("report.docx"),Click(Save_Button),ReadPrompt("Are you sure?").
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Methods (M):
- Definition: A method is a well-learned, pre-defined, and practiced sequence of operators and sub-goals that an expert user employs to achieve a specific goal.
- Efficiency: Methods describe a particular, efficient "how-to" for performing a task, representing the expert user's optimized interaction.
- Multiple Methods: A single goal can often be achieved by multiple distinct methods (e.g., saving a file via menu, toolbar button, or keyboard shortcut), each being a unique sequence.
- Example: For
GOAL: Delete-Word, one method might beMouse-Select-and-Menu-Delete(involvingMoveMouse,DragMouse, and sub-goals for menu access), while another isKeyboard-Shortcut-Delete(involvingPressKeyoperators).
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Selection Rules (S):
- Definition: These are rules that specify precisely which method to choose when there is more than one available method for achieving a given goal.
- Decision Criteria: They typically involve "If-Then" conditions that guide the choice based on contextual cues, system state, or personal preferences, reflecting the expert user's decision-making process.
- Purpose: Selection rules resolve ambiguity when multiple efficient paths exist, ensuring the model accurately predicts the specific sequence an expert would follow.
- Example: For
GOAL: Save-File:IF hands are on keyboard AND no mouse is available, THEN choose Keyboard-Shortcut-Method.
In essence, GOMS provides a structured way to represent an expert user's cognitive and motor knowledge, allowing for a deeper analysis and understanding of complex task execution beyond simple timing predictions.
Detailed
Detailed Summary of the Comprehensive Components of the GOMS Model
The GOMS (Goals, Operators, Methods, Selection Rules) model is a sophisticated, hierarchical cognitive model that builds upon simpler models like KLM. It explicitly represents the knowledge an expert user possesses to effectively interact with a system and accomplish tasks. This section meticulously defines each of its four core components:
-
Goals (G):
- Definition: Goals are the high-level objectives or intentions that drive user interaction. They represent what the user wants to achieve.
- Nature: They are declarative statements of intent and can be broken down into nested sub-goals, forming a hierarchical structure.
- Examples:
GOAL: Edit-Document,GOAL: Send-Email,GOAL: Print-Document.
-
Operators (O):
- Definition: Operators are the basic, atomic (unanalyzable) perceptual, cognitive, and motor actions performed by a user, or actions performed by the system, to work towards a goal.
- Categorization: They can be internal (cognitive/perceptual, e.g.,
Recall-Command,Read-Text) or external (motor, e.g.,Type-Character,Click-Mouse). System responses (System-Response-Time) are also included. - Relationship to KLM: KLM's operators (K, P, H, M, R) are a subset of the operators used in a full GOMS model, which allows for a richer and more context-specific set.
- Examples:
TypeString("report.docx"),Click(Save_Button),ReadPrompt("Are you sure?").
-
Methods (M):
- Definition: A method is a well-learned, pre-defined, and practiced sequence of operators and sub-goals that an expert user employs to achieve a specific goal.
- Efficiency: Methods describe a particular, efficient "how-to" for performing a task, representing the expert user's optimized interaction.
- Multiple Methods: A single goal can often be achieved by multiple distinct methods (e.g., saving a file via menu, toolbar button, or keyboard shortcut), each being a unique sequence.
- Example: For
GOAL: Delete-Word, one method might beMouse-Select-and-Menu-Delete(involvingMoveMouse,DragMouse, and sub-goals for menu access), while another isKeyboard-Shortcut-Delete(involvingPressKeyoperators).
-
Selection Rules (S):
- Definition: These are rules that specify precisely which method to choose when there is more than one available method for achieving a given goal.
- Decision Criteria: They typically involve "If-Then" conditions that guide the choice based on contextual cues, system state, or personal preferences, reflecting the expert user's decision-making process.
- Purpose: Selection rules resolve ambiguity when multiple efficient paths exist, ensuring the model accurately predicts the specific sequence an expert would follow.
- Example: For
GOAL: Save-File:IF hands are on keyboard AND no mouse is available, THEN choose Keyboard-Shortcut-Method.
In essence, GOMS provides a structured way to represent an expert user's cognitive and motor knowledge, allowing for a deeper analysis and understanding of complex task execution beyond simple timing predictions.
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The GOMS Model: An Overview
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Chapter Content
This lecture introduces the comprehensive GOMS (Goals, Operators, Methods, Selection Rules) model, a more sophisticated and hierarchical cognitive model than KLM. We will meticulously explore each of its components, understand how it explicitly represents and structures user knowledge, and discuss its powerful application in predicting, analyzing, and profoundly understanding more complex task execution.
Detailed Explanation
This segment sets the stage for understanding GOMS as an advanced cognitive model, building on the simpler KLM. It emphasizes that GOMS provides a structured way to represent an expert user's knowledge and actions, crucial for analyzing complex tasks. The key takeaway is the exploration of its four core components: Goals, Operators, Methods, and Selection Rules, which together offer a comprehensive framework for predicting and understanding user performance.
Examples & Analogies
Imagine GOMS as a detailed recipe book for an expert chef. Instead of just listing ingredients (like KLM's operators), it defines the dish (Goal), the individual actions (Operators), the step-by-step instructions for making a dish (Methods), and rules for choosing which dish to make based on ingredients or occasion (Selection Rules).
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- Chunk Title: Goals: The User's Objectives
- Chunk Text: Goals (G): These represent what the user desires to achieve. Goals are the high-level objectives or intentions that drive user interaction. They can be broken down into nested sub-goals, forming a hierarchy.
- Detailed Explanation: This chunk focuses on "Goals," the first component of GOMS. It clarifies that goals are the user's ultimate objectives or intentions, defining what the user wants to accomplish. The concept of hierarchical goals (main goals broken into sub-goals) is introduced, demonstrating how complex tasks are structured from a user's perspective.
- Real-Life Example or Analogy: Think of a project manager's task list. The main project (e.g., "Launch New Product") is the high-level Goal. This breaks down into smaller sub-goals like "Develop Marketing Campaign," "Finalize Production," and "Organize Launch Event."
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- Chunk Title: Operators: The Atomic Actions
- Chunk Text: Operators (O): These are the basic perceptual, cognitive, and motor actions that a user performs, or that the system performs, to work towards achieving a goal. Operators are the atomic, unanalyzable actions within the model.
- Detailed Explanation: This segment explains "Operators," the second GOMS component. It defines them as the most fundamental, indivisible actions a user (or system) performs. It distinguishes between internal (cognitive/perceptual) and external (motor) operators, and notes that system responses are also included. It also highlights that KLM's operators are a subset of the broader GOMS operator set.
- Real-Life Example or Analogy: Consider building with LEGOs. The individual LEGO bricks are the Operators β they are the smallest, unanalyzable units you use to build something. You can't break them down further.
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- Chunk Title: Methods: The "How-To" Sequences
- Chunk Text: Methods (M): A method is a well-learned, pre-defined, and practiced sequence of operators and sub-goals that can be employed to achieve a specific goal. A method describes a particular, efficient "how-to" for performing a task.
- Detailed Explanation: This chunk delves into "Methods," the third GOMS component. It defines a method as a pre-defined, efficient sequence of operators and sub-goals that an expert user follows to achieve a specific goal. The key idea is that methods represent the expert's optimized way of interacting, and that a single goal can often have multiple methods, providing flexibility.
- Real-Life Example or Analogy: If your Goal is "Make Coffee," a Method could be "Use French Press" (which involves specific steps like grind beans, boil water, pour, press) or "Use Drip Machine" (different steps). Both achieve the same goal, but through different sequences of actions.
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- Chunk Title: Selection Rules: Choosing the Right Method
- Chunk Text: Selection Rules (S): These are rules that specify precisely which method to choose when there is more than one available method for achieving a given goal. Selection rules reflect the expert user's decision-making process based on contextual cues, system state, or personal preferences.
- Detailed Explanation: This final segment explains "Selection Rules," the fourth GOMS component. It clarifies their role in resolving ambiguity when multiple methods exist for a goal. Selection rules are "If-Then" conditions that guide the expert user's choice based on context, system state, or learned preferences, making the GOMS model more precise in predicting actual user behavior.
- Real-Life Example or Analogy: Continuing the coffee analogy: A Selection Rule might be "IF I have less than 5 minutes, THEN choose 'Instant Coffee Method'." "ELSE IF I want the best taste, THEN choose 'French Press Method'." These rules dictate the choice of method based on specific conditions.
Key Concepts
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Hierarchical Representation: GOMS structures user knowledge and task execution from high-level goals down to atomic operators.
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Explicit Cognitive Modeling: GOMS explicitly models decision-making and planning, unlike simpler models.
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Expert User Focus: Like KLM, GOMS is primarily for analyzing highly practiced, error-free performance of expert users.
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Multiple Paths to Goals: GOMS acknowledges that users may have different methods to achieve the same goal.
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Contextual Decision Making: Selection Rules incorporate contextual factors into method choice.
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Examples
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Goal Hierarchy:
GOAL: Prepare-Presentation-\>GOAL: Create-Slides-\>GOAL: Insert-Image-\>GOAL: Resize-Image. -
Operators:
Click(File_Menu),TypeString("MyReport"),ScanScreen(for_icon),Wait(System_Response). -
Methods:
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For
GOAL: Copy-Text: -
Method 1:
Select-Text-\>Right-Click-\>Click(Copy_Option) -
Method 2:
Select-Text-\>PressKey(Ctrl)-\>PressKey(C) -
Selection Rule:
IF current task involves extensive typing, THEN choose Keyboard-Shortcut-Method for common operations ELSE choose Mouse-Menu-Method. -
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Flashcards
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Term: Goals (G)
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Definition: The user's objectives or intentions in the GOMS model.
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Term: Operators (O)
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Definition: Basic, atomic actions (perceptual, cognitive, motor, or system responses) in the GOMS model.
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Term: Methods (M)
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Definition: A well-learned sequence of operators and sub-goals to achieve a specific goal in GOMS.
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Term: Selection Rules (S)
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Definition: Rules in GOMS that specify which method to choose when multiple methods are available for a goal.
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Memory Aids
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Rhyme: Goals are the aims, Operators the plays, Methods the how-to, in expert user ways. Selection rules choose, when options abound, for tasks to be done, all around.
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Story: Imagine a master chef (expert user) planning a complex meal (Goal). They break it down into courses (sub-goals). For each dish, they have precise actions (Operators) like chopping or stirring. They also have practiced ways of making each dish (Methods), like a quick stir-fry or a slow braise. And depending on the time or ingredients, they have rules (Selection Rules) for which method to pick.
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Mnemonic: Go Over Methods, Select Rules.
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Acronym: GOMS = Goals, Operators, Methods, Selection Rules.
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Alternative Content
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Analogy: Think of GOMS as a detailed instruction manual for a highly skilled robot. The manual doesn't just list individual button presses (KLM); it defines the robot's ultimate mission (Goals), its basic movements (Operators), the complete procedures for specific tasks (Methods), and even rules for deciding which procedure to use based on the situation (Selection Rules).
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Visual Description: Imagine a flowchart. The top node is a Goal. Branches lead to different Methods. Each Method is a sequence of smaller boxes (Operators) and perhaps other Goals (sub-goals). At points where multiple Method branches emerge from a Goal, there's a diamond-shaped decision node representing the Selection Rules.
Examples & Applications
Goal Hierarchy: GOAL: Prepare-Presentation -\> GOAL: Create-Slides -\> GOAL: Insert-Image -\> GOAL: Resize-Image.
Operators: Click(File_Menu), TypeString("MyReport"), ScanScreen(for_icon), Wait(System_Response).
Methods:
For GOAL: Copy-Text:
Method 1: Select-Text -\> Right-Click -\> Click(Copy_Option)
Method 2: Select-Text -\> PressKey(Ctrl) -\> PressKey(C)
Selection Rule: IF current task involves extensive typing, THEN choose Keyboard-Shortcut-Method for common operations ELSE choose Mouse-Menu-Method.
Flashcards
Term: Goals (G)
Definition: The user's objectives or intentions in the GOMS model.
Term: Operators (O)
Definition: Basic, atomic actions (perceptual, cognitive, motor, or system responses) in the GOMS model.
Term: Methods (M)
Definition: A well-learned sequence of operators and sub-goals to achieve a specific goal in GOMS.
Term: Selection Rules (S)
Definition: Rules in GOMS that specify which method to choose when multiple methods are available for a goal.
Memory Aids
Rhyme: Goals are the aims, Operators the plays, Methods the how-to, in expert user ways. Selection rules choose, when options abound, for tasks to be done, all around.
Story: Imagine a master chef (expert user) planning a complex meal (Goal). They break it down into courses (sub-goals). For each dish, they have precise actions (Operators) like chopping or stirring. They also have practiced ways of making each dish (Methods), like a quick stir-fry or a slow braise. And depending on the time or ingredients, they have rules (Selection Rules) for which method to pick.
Mnemonic: Go Over Methods, Select Rules.
Acronym: GOMS = Goals, Operators, Methods, Selection Rules.
Alternative Content
Analogy: Think of GOMS as a detailed instruction manual for a highly skilled robot. The manual doesn't just list individual button presses (KLM); it defines the robot's ultimate mission (Goals), its basic movements (Operators), the complete procedures for specific tasks (Methods), and even rules for deciding which procedure to use based on the situation (Selection Rules).
Visual Description: Imagine a flowchart. The top node is a Goal. Branches lead to different Methods. Each Method is a sequence of smaller boxes (Operators) and perhaps other Goals (sub-goals). At points where multiple Method branches emerge from a Goal, there's a diamond-shaped decision node representing the Selection Rules.
Memory Aids
Interactive tools to help you remember key concepts
Acronyms
GOMS = Goals, Operators, Methods, Selection Rules.
Analogies
Think of GOMS as a detailed instruction manual for a highly skilled robot. The manual doesn't just list individual button presses (KLM); it defines the robot's ultimate mission (Goals), its basic movements (Operators), the complete procedures for specific tasks (Methods), and even rules for deciding which procedure to use based on the situation (Selection Rules).
- Visual Description
Flash Cards
Glossary
- Selection Rules (S)
Rules that specify which method to choose when multiple methods are available for a given goal.
- Contextual Decision Making
Selection Rules incorporate contextual factors into method choice.
- Selection Rule
IF current task involves extensive typing, THEN choose Keyboard-Shortcut-Method for common operations ELSE choose Mouse-Menu-Method.
- Definition
Rules in GOMS that specify which method to choose when multiple methods are available for a goal.
- Acronym
GOMS = Goals, Operators, Methods, Selection Rules.
- Visual Description
Imagine a flowchart. The top node is a Goal. Branches lead to different Methods. Each Method is a sequence of smaller boxes (Operators) and perhaps other Goals (sub-goals). At points where multiple Method branches emerge from a Goal, there's a diamond-shaped decision node representing the Selection Rules.