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

# Composite topic parameters

> Composite topic files define configuration for querying across two or more topics.

<Note>
  **Composite topics are currently in beta.** Reach out to your Omni contact or Omni support to opt into the beta.
</Note>

Composite topics are defined in `.composite_topic` files. The parameters below configure which topics are combined and how their fields align. For an overview and setup guide, see [Composite topics](/modeling/composite-topics).

| Parameter                                                                                 | Description                                                                                                                                     |
| ----------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------- |
| [topics](/modeling/composite-topics/parameters/topics)                                    | **Required**. The two or more topics to combine.                                                                                                |
| [always\_join\_all\_topics](/modeling/composite-topics/parameters/always-join-all-topics) | Controls whether all topics are included in the FULL OUTER JOIN or only those with selected fields. Defaults to `false` for better performance. |
| [fields](/modeling/composite-topics/parameters/fields)                                    | Curates which fields each sub-topic contributes to the field picker.                                                                            |
| [label](/modeling/composite-topics/parameters/label)                                      | Defines a display name for the composite topic.                                                                                                 |
| [description](/modeling/composite-topics/parameters/description)                          | Free text describing the composite topic, shown in the topic picker.                                                                            |
| [sample\_queries](/modeling/composite-topics/parameters/sample-queries)                   | Defines sample queries that can be performed on the composite topic, used by the Omni Agent and shown as examples.                              |
| [shared\_dimensions](/modeling/composite-topics/parameters/shared-dimensions)             | Defines cross-topic join keys that align the included topics.                                                                                   |
| [shared\_measures](/modeling/composite-topics/parameters/shared-measures)                 | Defines measures that combine values across topics after the join.                                                                              |
| [shared\_views](/modeling/composite-topics/parameters/shared-views)                       | Dimension tables joinable from every included topic, such as a date spine.                                                                      |