I think this one from the MODeL Reference Manual clearly States
the purpose of using define internal database name .
"""Each database vendor defines the physical constraints for naming
database items. In some cases these constraints prohibit the
generation of unique database names from MODeL names. Therefore, the
names defined in MODeL are explicitly translated to internal names,
which are then used to generate database names. Generating these
internal names removes the constraints imposed by the vendors and
enables MODeL definitions to be more verbose."""
thanks,
vijay.