# XPath

Orbeon Forms uses [XPath 2.0](https://www.w3.org/TR/xpath20/) as expression language.

This page and sub-pages describe XPath usage and the Orbeon Forms XPath function library. The documentation is split into:

* [Type annotations](/xforms/xpath/type-annotations.md)
* [Tips](/xforms/xpath/tips.md)
* [Compatibility](/xforms/xpath/compatibility.md)
* [Standard Functions](/xforms/xpath/standard-functions.md)
* [Maps and arrays Functions](/xforms/xpath/maps-arrays.md)
* Extension Functions
  * [Core functions](/xforms/xpath/extension-functions/extension-core.md)
  * [Utility functions](/xforms/xpath/extension-functions/extension-util.md)
  * [Model functions](/xforms/xpath/extension-functions/extension-model.md)
  * [Controls functions](/xforms/xpath/extension-functions/extension-controls.md)
  * [XML functions](/xforms/xpath/extension-functions/extension-xml.md)
  * [JSON functions](/xforms/xpath/extension-functions/extension-json.md)
  * [HTTP functions](/xforms/xpath/extension-functions/extension-http.md)
  * [Form Runner functions](/xforms/xpath/extension-functions/extension-form-runner.md)
  * [Other functions](/xforms/xpath/extension-functions/extension-other.md)
  * [Deprecated functions](/xforms/xpath/extension-functions/deprecated-functions.md)


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# 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://doc.orbeon.com/xforms/xpath.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.