> For the complete documentation index, see [llms.txt](https://cortex-docs.paloaltonetworks.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://cortex-docs.paloaltonetworks.com/cortex-xdr-3.x/cortex-xdr-3.x-documentation/data-management/parsing-rules/parsing-rules-file-structure-and-syntax/rule.md).

# RULE

Rules are very similar to functions in modern programming languages. They are essentially pieces of Cortex Query Language (XQL) syntax, tagged with a name - alias, for easier code reuse and avoiding code duplications. A `RULE` is an add-on to the Parsing Rule syntax and is optional to configure.

`RULE` syntax is derived from XQL with a few modifications as explained in the [Parsing Rules syntax](/cortex-xdr-3.x/cortex-xdr-3.x-documentation/data-management/parsing-rules/parsing-rules-file-structure-and-syntax.md).

{% hint style="info" %}

### Note

For more information on the XQL syntax, see [Get started with XQL](/cortex-xdr-3.x/cortex-xdr-3.x-documentation/cortex-xdr-xql/get-started-with-xql.md).
{% endhint %}

A few more points to keep in mind when writing `RULE` sections.

* Rules are defined by `[rule:ruleName]` as depicted in the following example:

  ```programlisting
  [rule:filter_alerts]
  filter raw_log not contains "alert";
  ```
* Rules are invoked by using a `call` keyword as depicted in the following example:

  ```programlisting
  [rule:filter_alerts]
  filter raw_log not contains "alert"; 
  [rule:use_another_rule]
  filter severity="LOW" | call filter_alerts | fields - raw_log;
  ```

  This is equivalent to writing:

  ```programlisting
  [rule:use_another_rule]
  filter severity="LOW" | filter raw_log not contains "alert" | fields - raw_log;
  ```
* Rule names are not case-sensitive. They can be written in any user-desired casing, such as UPPER\_SNAKE, lower\_snake, camelCase, and CamelCase). For example, `MY_RULE=My_Rule=my_rule`.
* Rule names must be unique across the entire file. This means you cannot have the same rule name defined more than once in the same file.
* Since section order is unimportant, you do not have to declare a `rule` before using it. You can have the `rule` definition section written below other sections that use this rule.
* You can add a single tag to the ingested data as part of the ingestion flow that you can easily query. You can add tags using both the `INGEST` and `RULE` sections.

  Example:

  Adding a single tag:

  ```programlisting
  [INGEST:vendor="Check Point", product="Anti Malware", target_dataset="malware_test", no_hit= drop  , ingestnull = true ]
  alter xx = call new_tag_rule; 
  ```

  ```programlisting
  [RULE:new_tag_rule]
  tag add "test";
  ```

  Example: 

  Adding a list of tags:

  ```programlisting
  [INGEST:vendor="Check Point", product="Anti Malware", target_dataset="malware_test", no_hit= drop  , ingestnull = true ]
  alter xx = call new_tag_rule; 
  ```

  ```programlisting
  [RULE:new_tag_rule]
  tag add "test1", "test2", "test3";
  ```

  <div data-gb-custom-block data-tag="hint" data-style="info" class="hint hint-info"><h3>Note</h3><p>You can also add tags using only the <code>INGEST</code> section. For more information, see <a href="/pages/jCBJmjGYV05VhFUDFeo5">INGEST</a>.</p></div>


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