xjc type definition name resolution error

I am running into troubles when wanting to compile my XSDs (which I am not the author of) with XJC.

Specifically, I get the error (there are actually more like these):

 [ERROR] src-resolve: Cannot resolve the name "ifopt:CountryRefStructure" to a(n) 'type definition' component.
   line 131 of file:/E:/ansdef/schema/siri-1.3/siri/siri_situationIdentity-v1.1.xsd

That is strange since the mentioned file (siri_situationIdentity-v1.1.xsd) refers to another XSD where the suspicious type is declared.

I tried several things

switch Java version to get different xjc
tried some different xjc directly from java.net
applied some modifications to the files so that the currently applied JAXB workarounds regarding includes/imports are removed
tried to use the whole directory with dependent schemas as target for xjc
Altova XMLSpy Java code generation works well without errors (but is no way to go for me)

None of them worked.

Does anybody have a clue what the error message is caused by? I don't see the point. You may get all the XSDs directly from here: Verband Deutscher Verkehrsunternehmen (VDV) - Ist-Daten-Schnittstellen

The command line I tried (amongst others) was:

xjc -readOnly -d generated -npa -target 2.1 -verbose VDV453_incl_454_V2.3e.xsd

Any help or hint is greatly appreciated.

Regards

Solution

The solution here was to use the -nv switch to disable strict validation.