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Spoon plugins provide developers the ability to add new or modify existing functionality of the Spoon UI. A Spoon plugin can modify any area that's been written in Pentaho XUL Xul Developer's Guide (http://wiki.pentaho.com/display/ServerDoc2x/The+Pentaho+XUL+Framework+Developer's+Guide). They can also provide whole new areas of funtionality to Spoon through the concept of a Spoon Perspective, which is not limited to XUL.
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