plugins/org.eclipse.app4mc.amalthea.model.editor.contribution/plugin.xml

<?xml version="1.0" encoding="UTF-8"?>
<plugin>

   <extension
         id="org.eclipse.app4mc.amalthea.model.editor.contribution.fragment"
         point="org.eclipse.e4.workbench.model">
      <fragment
            uri="fragment.e4xmi"
            apply="always">
      </fragment>
   </extension>

</plugin>