The API for "plug-ins", which are code modules that can be assigned to buttons and menu items. The name "plug-in" is really a misnomer because even built-in buttons and menu items are plug-ins -- a better term would have been "action". Third parties may "plug-in" their own plug-ins by creating a jar file with an Extension class @see com.vividsolutions.jump.workbench.plugin.Extension @see com.vividsolutions.jump.workbench.ui.plugin