We should really be looking into upgrading emf, so we can use the same version for all of emf.
Starting from version 2.7.0.v20120123-0926, both ecore and xmi use the same version.
ecore versions:
  https://repository.jboss.org/nexus/index.html#nexus-search;gav~~org.eclipse.emf.ecore~~~
xmi versions:
  https://repository.jboss.org/nexus/index.html#nexus-search;gav~~org.eclipse.emf.ecore.xmi~~~