Th project Ptidej UI Viewer Extensions provides the ptidej.viewer.extension.IViewerExtension interface that any extension to the viewers must implement. Differently from the ptidej.ui.analysis.IUIAnalysis interfaces defined in the Ptidej UI Analyses project, this interfaces requires an extension to implement a invoke(IRepresentation) method. Therefore, it is possible for an extension to access the source paths from which a PADL model has been built, found occurrences, and so on.