Most applications will be satisfied with the supported target lists. However, some applications may want to support additional targets. In fact, this is the primary reason for using UTM.
Consider the XmDrawingArea widget. This widget does not know how to convert any targets. Therefore, the standard XmDrawingArea cannot serve as a useful source for data transfer. However, XmDrawingArea does provide a UTM infrastructure. This infrastructure allows an application programmer to use UTM to supplement the data transfer capabilities of XmDrawingArea. For example, an application could supplement XmDrawingArea such that a user could copy text from an XmText widget to an XmDrawingArea widget. Similarly, an application could supplement XmDrawingArea such that a user could copy a pixmap from one XmDrawingArea to another.