# Plug-in configuration file

The plugin.xml controls all aspects of a plug-in, making each extension visible to the rest of the toolkit. The file uses pre-defined extension points to locate changes, and integrates those changes into the core code.

The root element of the plugin.xml file is `<plugin>`, and must specify an `id` attribute. The `id` attribute is used to identify the plugin, as well as to identify whether pre-requisite plugins are available. The `id` attribute should follow the syntax rules:

    id    ::= token('.'token)*
    token ::= ( [0..9] | [a..zA..Z] | ’_’ | ’-’ )+

The `<plugin>` element supports the following child elements:

- `<feature>` defines an extension to contribute to a defined extension point. The following attributes are supported:

  Attribute | Description | Required
  --- | --- | ---
  `extension` | extension point identifier | yes
  `value` | comma separated string value of the extension | either `value` or `file`
  `file` | file path value of the extension, relative to plugin.xml | either `value` or `file`
  `type` | type of the `value` attribute | no

- `<require>` defines plug-in dependencies. The following attributes are supported:

  Attribute | Description | Required
  --- | --- | ---
  `plugin` | vertical bar separated list of plug-ins that are required | yes
  `importance` | flag whether plug-in is required or optional | no

- `<template>` defines files that should be treated as templates. The following attributes are supported:

  Attribute | Description | Required
  --- | --- | ---
  `file` | file path to the template, relative to plugin.xml | yes

- `<meta>` defines metadata. The following attributes are supported:

  Attribute | Description | Required
  --- | --- | ---
  `type` | metadata name | yes
  `value` | metadata value | yes

Any extension that is not recognized by the DITA-OT is ignored; all elements other than `<plugin>` are optional. Since version 1.5.3 multiple extension definitions within a plugin configuration file are combined; in older versions only the last extension definition is used.

Parent topic: Creating DITA-OT plug-ins