> ## Documentation Index
> Fetch the complete documentation index at: https://docs.siftstack.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Step 1: Create a Rule

export const SiftIcon = ({className}) => <span className={`inline-flex items-center align-middle text-black dark:text-white ${className || ''}`}>
    <svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" version="1.1" id="Artwork" x="0px" y="0px" viewBox="0 0 1005.58 733.96" style={{
  enableBackground: "new 0 0 1005.58 733.96",
  width: "2em",
  height: "2em"
}} xmlSpace="preserve">
      <path fill="currentColor" d="M552.16,150.89c-165.6,0-180.29,160.61-300.62,192.32v2.67h601.24v-2.67C747.74,324.18,717.72,150.89,552.16,150.89z   M453.46,583.08c165.6,0,180.29-160.61,300.62-192.32v-2.67H152.84v2.67C257.88,409.78,287.91,583.08,453.46,583.08z" />
    </svg>
  </span>;

## Overview

Let's discuss and create a Rule in Sift, which enables you to create logical conditions to evaluate your telemetry.

## What are Rules

Rules in Sift are logical conditions, defined using the Common Expression Language (CEL), that evaluate telemetry across one or more Channels from an Asset to detect behaviors, anomalies, and threshold breaches in live and historical data.

* When a Rule evaluates to true, it can create Annotations, send notifications, or be assigned to a user for follow-up
* Rules support versioning and previewing against existing Run data

## Preview and create a Rule

To better understand Rules, let's create one that captures a specific behavior in a Channel from the low Earth orbit satellite (LEO) we explored in [Tutorial 1](../tutorial-1/overview).

Specifically, we'll create a Rule for the temperature Channel in the **camera\_1** subsystem that triggers an Annotation when the temperature exceeds **30** degrees Celsius.

This ensures future datasets are automatically checked for similar anomalies and flagged for review.

1. In **Sift's** home page, click the <Icon icon="code-simple" /> **Rules** tab.
2. Click **New Rule**.
3. In the **Rule name** box, enter the following:
   ```
   fl_tutorial_4_rule
   ```
4. Replace `fl` (in `fl_tutorial_4_rule`) with your own initials.
5. In the **Asset name**, select the Asset created in [Tutorial 1](../tutorial-1/overview).
   * **For example**: fl\_tutorial\_1\_asset
6. In the **Input Channels** list, select the following Channel:
   * **camera\_1.temperature**
7. In the **Enter an expression** box, enter:
   ```
   $1 > 30
   ```
   * **Channel references**:  Selected Channels are referenced in the expression using `$1`, `$2`, `$3`, and so on, in the order they appear in the **Input Channels** list. In this case, `$1` refers to **camera\_1.temperature**.
   * **Functions**: Expressions support a variety of built-in function types for different kinds of calculations. To browse all available functions, observe the **Expression Syntax** section.
8. Click **Select Run(s) to preview**.
9. Click the Run created in [Tutorial 1](../tutorial-1/overview).
   * **For example**: fl\_tutorial\_1\_run
10. Click **Preview 1 Runs**.
11. Click **Save**.