in util/src/main/java/org/apache/jsieve/util/XmlOut.java [643:651]
private CharSequence toName(CharSequence localName, CharSequence uri, CharSequence prefix) {
final CharSequence name;
if (prefix == null || "".equals(prefix) || uri == null || "".equals(uri)) {
name = localName;
} else {
name = prefix + ":" + localName;
}
return name;
}