I change this to be suspended. A proper fix will be done in 6.4 when we will support multiple roots for the testing tool.

Now the schema only allow one root which is correct (Note that according to W3C, default value of maxOccurs is 1). However, EiffelStudio should report when there are multiple ones. But for now, again because in 6.4 we will support multiple roots, we decide to leave it as it is.

Yes, cluster, class, feature and all_classes attributes of root element are not well done in this way. Instead, we should use elements instead of attributes to describe constrains among these options. Because XML schema does not support choice  between attributes.