Notebook Structure

To build effective extensions, it's important to understand how XulHub organizes content. A XulHub Notebook is a hierarchical structure of metadata and cells.

The Hierarchy

1. Notebook: The top-level document (e.g., "Biology 101").
2. Cell: A single unit of content or an exercise within the notebook.
3. Content Block: Individual items inside a cell (Text, Images, YouTube, or Third-Party Extensions).

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1. Notebook Metadata

Every notebook has metadata that describes its state, ownership, and configuration.

• Name/Title: The name of the notebook.
• Published: Whether the notebook is in draft or live mode.
• Category: Determines the general behavior (e.g., mixed, quiz).

2. Cells

A notebook is composed of an array of cells. Each cell has:

• cellType: Either 'notes' (purely instructional) or 'question' (graded).
• label: A label for the cell (e.g., "Q1", "Intro").
• contents: An array of different content blocks.

3. Third-Party Extension Block

This is where your SDK-powered application lives. Within the contents array of a cell, your extension appears as a block with the type thirdParty.

Data Structure of an Extension Block:

• source: The URL of your application (running in an iframe).
• extensionData: The actual JSON data you manage via sdk.saveContent() and receive in sdk.onReady().
• id: A unique identifier for the block instance.

Example representation:

{
  "cellType": "question",
  "label": "Vocabulary Check",
  "contents": [
    {
      "contentType": "text",
      "data": { "text": "Match the words with their definitions:" }
    },
    {
      "contentType": "thirdParty",
      "data": {
        "source": "https://my-exercise-app.com",
        "extensionData": {
          "pairs": [ { "word": "Apple", "def": "A red fruit" } ]
        },
        "id": "ext-123"
      }
    }
  ]
}

By understanding this structure, you can see that your extension sits alongside other standard XulHub blocks, allowing for a rich, mixed-media learning experience.