## Anchors

Anchors can be thought of as the extension point equivalent for user assistance documents. The same way components use extension points to allow other components to extend their functionality, documents can use anchors to allow other components to extend their user assistance content.

Let's say component A's documentation provides a listing of file formats it supports. If component B extends A's support to several more formats, you can place an anchor in A's list, and extend the list from B. For example:

       <p>The following list shows the supported formats:</p>
       <ul>
          <li>Portable Network Graphics (.png)</li>
          <li>Joint Photographic Experts Group (.jpeg)</li>
          <li>Graphical Interchange Format (.gif)</li>

          <!-- Extra formats go here -->
          <anchor id="image_format_list"/>
       </ul>

Then component B can make a contribution to the anchor to add more formats to the list.

### How do I contribute content into an anchor?

This depends on the type of document. Generally you define an extension that points to an XML file containing the content to be added. Follow the links in the section below to learn how to do it in the document type you're using:

### Where can I use anchors?

See below for a list of the document types in which includes can be used. The format of the `path` element of the include depends on the type of document you're including from. As you can see in the example above, the format for XHTML help documents is "`<plugin_id>/<path_to_file>/<element_id>`". Refer to the links below for the format for your document type.

- Welcome/Intro XML
- Welcome/Intro XHTML
- Help XHTML