XMI24 — Allow for ‘tight’ schemas

If a metamodel has multiple inheritance, XMI has no means to produce an XML Schema to restrict the target of a reference: it is always xsd:any.

Though in theory a metamodel can be extended, it is rarely the case.

Therefore there should be an option to produce an XSD that validates only instances of an unextended metamodel. In fact this should be the default.

There should be a new Boolean XMI tag org.omg.xmi.allowMetamodelExtension which defaults to ‘false’

This will affect section 4.8.5 and rules 4e and 4f of 5.2.1. And examples. If org.omg.xmi.allowMetamodelExtension is false (the default) then the type of the element will be a union of the metaclass typing the property and any subclass in the metamodel. Abstract classes will not be included.

If a metamodel has multiple inheritance, XMI has no means to produce an XML Schema to restrict the target of a reference: it is always xsd:any.
Though in theory a metamodel can be extended, it is rarely the case.
Therefore there should be an option to produce an XSD that validates only instances of an unextended metamodel. In fact this should be the default.
There should be a new Boolean XMI tag org.omg.xmi.allowMetamodelExtension which defaults to ‘false’

This will affect section 4.8.5 and rules 4e and 4f of 5.2.1. And examples.
If org.omg.xmi.allowMetamodelExtension is false (the default) then the type of the element will be a union of the metaclass typing the property and any subclass in the metamodel. Abstract classes will not be included.