A system and method for validating an extensible markup language (XML) document and reporting schema violations in real time. A parallel tree is maintained that includes nodes corresponding to non-native XML elements of the XML document. When changes occur to the XML document, the non-native XML elements corresponding to the changes are marked. The nodes corresponding the marked non-native XML elements are validated against an XML schema that corresponds to the non-native XML markup. The elements and nodes corresponding to errors in the non-native XML markup are then reported to the user according to display indicators in the XML document and the parallel tree.