xapi-specification（xapi 规范）

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

1. Actor - Agent or Group performing the action
2. Verb - Action taken (URI + display name)
3. 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:

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

Activity Types

Common activity types for educational contexts:

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

cmi5 Profile

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

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

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

Statement Generation Workflow

To generate a valid xAPI statement:

1. Identify the Actor (learner/user information)
2. Select appropriate Verb from ADL registry
3. Define the Object (activity being tracked)
4. Include Result for assessment outcomes
5. Add Context for hierarchical relationships
6. Generate UUID for statement ID
7. 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

External Resources

• xAPI Specification
• ADL Vocabulary
• cmi5 Specification