Plug-in dependencies A DITA-OT plug-in can be dependent on other plug-ins. Prerequisite plug-ins are installed first, which ensures that DITA-OT handles XSLT overrides correctly. require plug-insprerequisitesdependenciesorderrequire XSLTplug-ins

I'm not entirely happy with this topic as it currently is, but want to move forward with the overall rework.

The original topic was quite a mixture of task, concept, and reference. While it could have been reworked as a task topic, it really was about working with a plugin.xml file, not using an extension point.

I still wonder whether this topic would be better of as a reference topic in the reference section for the topic cluster.

The require element in the plugin.xml file specifies whether the plug-in has dependencies. Use require elements to specify prerequisite plug-ins, in order from most general to most specific.

If a prerequisite plug-in is missing, DITA-OT prints a warning during installation. To suppress the warning but keep the installation order if both plug-ins are present, add importance="optional" to the require element.

If a plug-in can depend on any one of several optional plug-ins, separate the plug-in IDs with a vertical bar. This is most useful when combined with importance="optional".

Example: Plug-in with a prerequisite plug-in

The following plug-in will only be installed if the plug-in with the ID com.example.primary is available. If that plug-in is not available, a warning is generated and the installation operation fails.

<plugin id="com.example.builds-on-primary"> <!-- ... Extensions here --> <require plugin="com.example.primary"/> </plugin> Example: Plug-in that has optional plug-ins

The following plug-in will only be installed if either the plug-in with the ID pluginA or the plug-in with the ID pluginB is available. If neither of those plug-ins are installed, a warning is generated but the installation operation is completed.

<plugin id="pluginC"> <!-- ...extensions here --> <require plugin="pluginA|pluginB" importance="optional"/> </plugin>

We need to check this example against the toolkit. Text in the original topic was wrong, but I have not tested this.