# Root & Stores

FMTC uses a *root* and *stores* to structure its data. In general, a single root exists (which uses a single [backend](/usage/initialisation.md#backends)), which contains multiple named stores. Cached tiles can belong to multiple stores, which reduces duplication and maximizes flexibility.

{% hint style="info" %}
The structures use the ambient backend when a method is invoked on it, not at construction time.

Therefore, it is possible to construct an `FMTCStore`/`FMTCRoot` before initialisation, but 'using' any methods on it will throw `RootUnavailable`.
{% endhint %}


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://fmtc.jaffaketchup.dev/usage/root-and-stores.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.