!!!plugin.xml

The general structure of the XML file is described in the [JPF tutorial|http://jpf.sourceforge.net/de/tutorial.html].
Therefore, we focus on the parts, that are specific for the d3web development.
A minimalistic example defining only one {{ExtensionPoint}} is given as follows:


%%prettify 
{{{
<?xml version="1.0" ?>
<!DOCTYPE plugin PUBLIC "-//JPF//Java Plug-in Manifest 1.0" "http://jpf.sourceforge.net/plugin_1_0.dtd">
<!-- This plugin only defines extension points for CasePersistenceHandler and CaseConversionHandler. -->
<plugin id="de.d3web.casepersistence" version="0.0.1">
	
	<extension-point id="CasePersistenceHandler">
		<parameter-def id="class" />
		<parameter-def id="name" />
		<parameter-def id="description" />
		<parameter-def id="version" />
		<parameter-def id="priority" type="number" />
	</extension-point>
	
</plugin>
}}}
/%

This plugin has the ID {{de.d3web.casepersistence}} and defines the {{ExtensionPoint}} "CasePersistenceHandler". 
In general, a plugin can define multiple extension points. 
Within the plugin, the IDs of the extension points have to be unique. 
However, two different plugins may use the same ID for different extension points, since the ID of an extension point is always evaluated together with the ID of the plugin.
This is shown by the following extension of the extension point above:

%%prettify 
{{{
<?xml version="1.0" ?>
<!DOCTYPE plugin PUBLIC "-//JPF//Java Plug-in Manifest 1.0" "http://jpf.sourceforge.net/plugin_1_0.dtd">
<plugin id="de.d3web.casepersistence.basic" version="0.0.1">
	
	<requires>
		<import plugin-id="de.d3web.cpers.xml" />
	</requires>
	
	<runtime>
		<library id="de.d3web.cpers.xml" path="." type="code">
			<export prefix="*" />
		</library>
	</runtime>
	
	<extension plugin-id="de.d3web.casepersistence" point-id="CasePersistenceHandler"
		id="FactHandler">
		<parameter id="class"
			value="de.d3web.cpers.xml.FactHandler" />
		<parameter id="name" value="FactHandler" />
		<parameter id="description" value="Handler for facts" />
		<parameter id="version" value="1.0" />
		<parameter id="priority" value="5" />
	</extension>
	
</plugin>
}}}
/%

A plugin can define new extension points, but can also extend existing extension points of other plugins.
The defined extension point specifies that each extension has to give values for class, name, description, version, and priority.
This has to be defined by each extension point; an extension point further can require additional value, for example the specification of a file name.