Xerlin supports two different kinds of plugins, DTD plugins and Action plugins. These plugins can be developed for application-specific uses of Xerlin as discussed in the Plugin Development Guide.
Plugins are usually a jar file which you simply install in the plugins directory of Xerlin. Xerlin 1.2 includes two example plugins, the example plugin, and the XSLT plugin. The Example plugin has a very simple DTD and one custom editor which allows you to pick a color from a color chooser. The XSLT plugin translates an xml document using a <?xml-stylesheet href="url"?> processing instruction.
For more information on plugins, and to download thirdparty plugins for Xerlin, see the Xerlin web site.
DTD Plugins provide a way to add DTDs to Xerlin's DTD Chooser, and special editing actions for specific DTDs. DTD plugins show up on the Help->About Plugins menu, but not on the Plugins menu itself. When you start a new document or edit an existing document with a PUBLIC identifier which is the same as one specified by a DTD plugin, the DTD and custom editors associated with that plugin are used. DTD plugins can also provide the SYSTEM identifer and the root element to use for that DTD.
The Xerlin Example plugin has a custom editor which appears where there is a color attribute on elements for that DTD as shown in Figure 5.1 This attribute would normally have a textbox where you can enter the hex value for a color, but with the example plugin, you get a button which allows you to use a graphical color chooser. The color you choose is converted to the hex notation and saved in the xml file in that format.