xAPI Specification Knowledge Base

Provide comprehensive guidance on xAPI (Experience API) specification for educational assessment and learning analytics.

Core Concepts

Statement Structure

An xAPI Statement follows the "Actor-Verb-Object" pattern with optional Result and Context:

{
  "actor": { },      // Who performed the action
  "verb": { },       // What action was performed
  "object": { },     // What was acted upon
  "result": { },     // Outcome of the action (optional)
  "context": { },    // Additional context (optional)
  "timestamp": "",   // When the action occurred
  "id": ""           // Unique statement identifier (UUID)
}

Required Fields

Actor - Agent or Group performing the action
Verb - Action taken (URI + display name)
Object - Activity, Agent, or Statement Reference

Actor Types

Agent (single learner):

{
  "objectType": "Agent",
  "name": "Learner Name",
  "mbox": "mailto:learner@example.com"
}

Account-based identification (recommended for LMS):

{
  "objectType": "Agent",
  "account": {
    "homePage": "https://lms.example.com",
    "name": "user123"
  }
}

Verb Structure

Define verbs with URI identifier and display text:

{
  "id": "http://adlnet.gov/expapi/verbs/answered",
  "display": {
    "en-US": "answered"
  }
}

Consult references/verbs.md for the complete ADL and cmi5 verb registry.

Object (Activity) Structure

{
  "objectType": "Activity",
  "id": "https://example.com/activities/quiz-123",
  "definition": {
    "name": { "en-US": "Quiz on xAPI Basics" },
    "description": { "en-US": "A quiz testing knowledge of xAPI" },
    "type": "http://adlnet.gov/expapi/activities/assessment"
  }
}

Result Structure

Capture assessment outcomes:

{
  "score": {
    "scaled": 0.85,
    "raw": 85,
    "min": 0,
    "max": 100
  },
  "success": true,
  "completion": true,
  "response": "choice-a",
  "duration": "PT30S"
}

Duration format: ISO 8601 duration (PT = Period Time, e.g., PT1H30M = 1 hour 30 minutes)

Context Structure

Provide additional information about the learning experience:

{
  "registration": "uuid-for-attempt",
  "contextActivities": {
    "parent": [{ "id": "https://example.com/course-123" }],
    "grouping": [{ "id": "https://example.com/program-abc" }],
    "category": [{ "id": "https://w3id.org/xapi/cmi5/context/categories/cmi5" }]
  },
  "platform": "Example LMS",
  "language": "en-US"
}

Interaction Types for Assessments

xAPI supports these interaction types for quiz questions:

Type	Description	Use Case
`true-false`	Binary choice	Yes/No, True/False questions
`choice`	Multiple choice	Single or multiple selection
`fill-in`	Text input	Short answer questions
`long-fill-in`	Long text	Essay questions
`matching`	Pair matching	Match items from two lists
`performance`	Task steps	Procedural tasks
`sequencing`	Order items	Arrange in correct sequence
`likert`	Scale rating	Survey/opinion questions
`numeric`	Number input	Mathematical answers

Consult references/interaction-types.md for detailed examples of each type.

Activity Types

Common activity types for educational contexts:

Category	Type URI	Use Case
Assessment	`http://adlnet.gov/expapi/activities/assessment`	Quizzes, exams
Question	`http://adlnet.gov/expapi/activities/cmi.interaction`	Individual questions
Course	`http://adlnet.gov/expapi/activities/course`	Course container
Module	`http://adlnet.gov/expapi/activities/module`	Course sections
Lesson	`http://adlnet.gov/expapi/activities/lesson`	Individual lessons

Consult references/activity-types.md for the complete registry.

cmi5 Profile

cmi5 is a standardized xAPI profile for e-learning. Key requirements:

Defined verbs: launched, initialized, completed, passed, failed, abandoned, waived, terminated
Mandatory context: registration, sessionId, masteryScore
Required extensions: sessionId, launchMode, launchURL

For cmi5-compliant statements, consult references/cmi5-profile.md.

Statement Generation Workflow

To generate a valid xAPI statement:

Identify the Actor (learner/user information)
Select appropriate Verb from ADL registry
Define the Object (activity being tracked)
Include Result for assessment outcomes
Add Context for hierarchical relationships
Generate UUID for statement ID
Add timestamp in ISO 8601 format

Validation Checklist

Validate statements against these criteria:

Structural validation:

Actor has valid identifier (mbox, account, or openid)
Verb has id (URI) and display (language map)
Object has id and objectType

Vocabulary validation:

Verb URI matches ADL/cmi5 registry
Activity type URI is valid

cmi5 validation:

Context includes registration UUID
Context includes sessionId extension
Correct verb sequence (launched → initialized → ... → terminated)

Interaction validation:

interactionType matches response format
correctResponsesPattern format matches interactionType
choices/scale/source/target arrays are valid for type

Additional Resources

Reference Files

Detailed specifications and registries:

references/verbs.md - Complete ADL and cmi5 verb registry
references/activity-types.md - Activity type URIs and usage
references/interaction-types.md - Detailed interaction type examples
references/cmi5-profile.md - cmi5 requirements and extensions

xAPI Specification