Pathological PEs in external DTD subset

Dear Sirs!

The XML specification (1.0 and 1.1, latest versions) allows the placement of parameter entity references in external DTD subsets in ways that are rather pathological. Although they normally do not occur in real documents, software would have to be able to deal with them in ways conforming to the standard.

I have written several short examples of such constructions that according to my understanding can all be considered as being allowed and valid by the XML specifiaction, yet, when tested with various widely-used validating XML parsers, lead to a variety of different results, depending on which software is used. It follows that either most of these software implementations do not conform to the standard or that the standard itself does not uniquely determine whether the tested examples are valid or not.

The examples together with the testing results can be found at http://www.floriankaeferboeck.at/XML/Comparison.html
If it is possible, please tell me which of the examples is valid according to the standard!

With best regards,
   Florian Käferböck