File Format

The .lotnb Format

LoT Notebook files use the .lotnb extension and follow a JSON-based structure compatible with VS Code’s notebook API. Each file contains an array of cells—documentation and code blocks that make up your notebook.

You don’t need to edit the JSON directly. VS Code’s notebook interface handles the structure automatically. This page is for understanding what’s happening under the hood.

File Structure

A .lotnb file is a JSON array where each element represents a cell:

[
  {
    "kind": 1,
    "language": "markdown",
    "value": "# My First Notebook\n\nThis is a markdown cell with documentation."
  },
  {
    "kind": 2,
    "language": "lot",
    "value": "DEFINE ACTION Heartbeat\nON EVERY 10 SECONDS DO\n    PUBLISH TOPIC \"system/heartbeat\" WITH TIMESTAMP \"UTC\""
  },
  {
    "kind": 2,
    "language": "python",
    "value": "# Script Name: DataProcessor\ndef calculate_average(values):\n    return sum(values) / len(values)"
  }
]

Cell Properties

Each cell has three required properties:

Property	Type	Description
`kind`	integer	Cell type: `1` = Markdown, `2` = Code
`language`	string	Cell language: `"markdown"`, `"lot"`, or `"python"`
`value`	string	Cell content (use `\n` for line breaks)

Kind Values

Kind	Type	Purpose
`1`	Markdown	Documentation, explanations, headers
`2`	Code	Executable LoT or Python code

Language Values

Language	Cell Kind	Description
`markdown`	1	Rich text documentation
`lot`	2	LoT definitions (Actions, Models, Routes, Rules)
`python`	2	Python scripts for broker execution

Cell Types in Detail

Markdown Cells

Markdown cells support standard Markdown syntax plus some extensions:

{
  "kind": 1,
  "language": "markdown",
  "value": "## Temperature Monitoring System\n\nThis notebook implements a complete temperature monitoring solution:\n\n- **Sensors**: Read from `sensors/+/temperature`\n- **Alerts**: Publish to `alerts/high-temp` when threshold exceeded\n- **Logging**: Store all readings in database\n\n### Architecture\n\n| Component | Topic | Purpose |\n|-----------|-------|--------|\n| Sensor Reader | sensors/+/temperature | Ingest data |\n| Alert Generator | alerts/+ | Notify operators |"
}

Supported Markdown features:

Headers (#, ##, ###)
Bold, italic, code formatting
Bullet and numbered lists
Tables
Code blocks (for examples, not execution)
Links and images

LoT Code Cells

LoT cells contain executable Language of Things definitions:

{
  "kind": 2,
  "language": "lot",
  "value": "DEFINE ACTION TemperatureMonitor\nON TOPIC \"sensors/+/temperature\" DO\n    SET \"sensor_id\" WITH TOPIC POSITION 2\n    IF PAYLOAD > 80 THEN\n        PUBLISH TOPIC \"alerts/high-temp/\" + {sensor_id} WITH \"Critical: \" + PAYLOAD + \"°C\""
}

Valid LoT definitions:

Definition	Syntax
Action	`DEFINE ACTION ActionName`
Model	`DEFINE MODEL ModelName WITH TOPIC "..."`
Route	`DEFINE ROUTE RouteName WITH TYPE ...`
Rule	`DEFINE RULE RuleName`

Python Cells

Python cells contain scripts that run inside the broker when called from LoT:

{
  "kind": 2,
  "language": "python",
  "value": "# Script Name: Validators\ndef validate_temperature(value, min_temp, max_temp):\n    \"\"\"Check if temperature is within acceptable range\"\"\"\n    try:\n        temp = float(value)\n        return {\n            \"valid\": min_temp <= temp <= max_temp,\n            \"value\": temp,\n            \"range\": f\"{min_temp}-{max_temp}\"\n        }\n    except (ValueError, TypeError):\n        return {\"valid\": False, \"error\": \"Invalid temperature value\"}"
}

Required format: Python scripts must start with # Script Name: YourScriptName as the first line. This header tells the broker how to register and reference the script.

Creating a New Notebook

Method 1: VS Code Interface

Create a new file with .lotnb extension
VS Code automatically opens it in notebook mode
Use the + Code and + Markdown buttons to add cells
Select cell language from the dropdown (lot, python, markdown)

Method 2: Manual Creation

Create a file with minimal JSON structure:

[
  {
    "kind": 1,
    "language": "markdown",
    "value": "# My Notebook\n\nAdd your documentation here."
  },
  {
    "kind": 2,
    "language": "lot",
    "value": "DEFINE ACTION MyFirstAction\nON EVERY 10 SECONDS DO\n    PUBLISH TOPIC \"test/hello\" WITH \"Hello World\""
  }
]

Save with .lotnb extension and open in VS Code.

Example: Complete Notebook

Here’s a full example showing all cell types working together:

[
  {
    "kind": 1,
    "language": "markdown",
    "value": "# Production Monitoring System\n\nThis notebook implements production line monitoring with:\n- Real-time part counting\n- Quality validation using Python\n- Alert generation for anomalies"
  },
  {
    "kind": 1,
    "language": "markdown",
    "value": "## Python Validators\n\nFirst, we define our validation functions:"
  },
  {
    "kind": 2,
    "language": "python",
    "value": "# Script Name: QualityChecker\ndef check_dimensions(length, width, tolerance=0.5):\n    \"\"\"Validate part dimensions against specifications\"\"\"\n    target_length = 100.0\n    target_width = 50.0\n    \n    length_ok = abs(float(length) - target_length) <= tolerance\n    width_ok = abs(float(width) - target_width) <= tolerance\n    \n    return {\n        \"passed\": length_ok and width_ok,\n        \"length_deviation\": float(length) - target_length,\n        \"width_deviation\": float(width) - target_width\n    }"
  },
  {
    "kind": 1,
    "language": "markdown",
    "value": "## Part Counter Action\n\nCounts produced parts and tracks hourly production:"
  },
  {
    "kind": 2,
    "language": "lot",
    "value": "DEFINE ACTION PartCounter\nON TOPIC \"production/line1/part-complete\" DO\n    SET \"count\" WITH (GET TOPIC \"production/line1/count\" AS INT) + 1\n    PUBLISH TOPIC \"production/line1/count\" WITH {count}\n    PUBLISH TOPIC \"production/line1/last-update\" WITH TIMESTAMP \"UTC\""
  },
  {
    "kind": 1,
    "language": "markdown",
    "value": "## Quality Check Action\n\nValidates each part using our Python function:"
  },
  {
    "kind": 2,
    "language": "lot",
    "value": "DEFINE ACTION QualityValidator\nON TOPIC \"production/line1/measurement\" DO\n    SET \"length\" WITH (GET JSON \"length\" IN PAYLOAD AS DOUBLE)\n    SET \"width\" WITH (GET JSON \"width\" IN PAYLOAD AS DOUBLE)\n    \n    CALL PYTHON \"QualityChecker.check_dimensions\"\n        WITH ({length}, {width})\n        RETURN AS {result}\n    \n    IF (GET JSON \"passed\" IN {result} AS BOOL) EQUALS TRUE THEN\n        PUBLISH TOPIC \"production/line1/quality/passed\" WITH {result}\n    ELSE\n        PUBLISH TOPIC \"production/line1/quality/failed\" WITH {result}\n        PUBLISH TOPIC \"alerts/quality\" WITH \"Part failed inspection\""
  }
]

Best Practices

Use descriptive markdown headers

Start notebooks with a title and overview. Use headers to organize sections logically.

One definition per code cell

Keep each Action, Model, Route, or Rule in its own cell. This makes debugging and selective execution easier.

Document before you code

Write a markdown cell explaining what the next code cell does before writing the code. This helps you think through the logic.

Use consistent naming

Follow a naming convention for your Actions, Models, and Python scripts. Example: SensorTemperatureMonitor, ProductionPartCounter.

Troubleshooting

File won't open as notebook?

Verify the file has .lotnb extension (not .lotnb.json)
Check that the LoT Notebooks extension is installed
Ensure the file contains valid JSON (use a JSON validator)

JSON syntax errors?

Common issues:

Missing commas between cells
Unescaped quotes in value strings (use \")
Unescaped newlines (use \n)
Missing closing brackets

Cell showing wrong language?

Check the language property matches the content type. VS Code should auto-detect, but you can manually switch using the language selector in the cell toolbar.

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Product Updates

The .lotnb Format

File Structure

Cell Properties

Kind Values

Language Values

Cell Types in Detail

Markdown Cells

LoT Code Cells

Python Cells

Creating a New Notebook

Method 1: VS Code Interface

Method 2: Manual Creation

Example: Complete Notebook

Best Practices

Troubleshooting

Next Steps

Getting Started

LoT Language Reference

​The .lotnb Format

​File Structure

​Cell Properties

​Kind Values

​Language Values

​Cell Types in Detail

​Markdown Cells

​LoT Code Cells

​Python Cells

​Creating a New Notebook

​Method 1: VS Code Interface

​Method 2: Manual Creation

​Example: Complete Notebook

​Best Practices

​Troubleshooting

​Next Steps

Getting Started

LoT Language Reference

The .lotnb Format

File Structure

Cell Properties

Kind Values

Language Values

Cell Types in Detail

Markdown Cells

LoT Code Cells

Python Cells

Creating a New Notebook

Method 1: VS Code Interface

Method 2: Manual Creation

Example: Complete Notebook

Best Practices

Troubleshooting

Next Steps