Missing mapping of extension tagged values jeopardises backwards compatibility

The two tragged values "extensionName" and "extensionVersion" are mapped to XML attributes for instances that are created from an extended schema. They are defined in that schema as XML attributes of the D2LogicalModel class.

The claim for level B extensions is that all valid instances are also valid against the "big" schema (i.e. as a reference).

The full schema does NOT contain the definition of the "extensionName" and "extensionVersion" XML attributes.

Hence, a valid of an extended schema that does have occurences of the "extensionName" or the "extensionVersion" XML attribute on the top level "d2LogicalModel" element does calidate against the extended schema but it does not against the full schema:

Proposed solution:
include optional XML attrbute defintions in section 4.5. alongside "modelBaseVersion"! Modify the tool accordingly! Attributes shouls be made mandatory when creating an extended schema.