".xmi" is just the default file extension for models serialized in XMI, but other extension names can also actually concern XMI files.
Notably, files with the ".uml" extension are also XMI files.
However, in the case of MoDisco (and of all the other Eclipse Modeling projects), the handled UML models conform to the UML metamodel as specified in Ecore by the Eclipse UML2 project.
If Modelio relies on another (proprietary or open) implementation of the UML metamodel, you will have to transform your models so that they conform to that specific implementation.
I hope this helps.
Thanks a lot for your answer. I have realized that the exported files with the ".uml" extension are also XMI files.Why can not the XMI file corresponding the standard be imported to other modeling tools now that the XMI file is the interchange standard for UML between modeling tools? Does the interchange failure stir up by incompatibility of xmi version? is it a very heavy workload if i must develop a tool to transform model? thanks again.
XMI is just a (standard) serialization format, what is important is actually the metamodel the models conform to.
If different tools are providing different implementations of the UML metamodel, then they logically cannot directly interoperate.
In that case, writing the transformation building the mapping between the two metamodel implementations/versions should be quite systematic (even it can be verbose).