XML is a very popular file format for describing many sorts of data. Is there a ready to use XML parser or you have to program the parser each time from scratch?
FET uses the Qt DOM XML parser. There are two parsers in Qt: DOM and SAX. See: http://doc.qt.nokia.com/4.7/qtxml.html . Also, see fet-v.v.v/src/engine/rules.cpp for XML reading of FET.