Consider the following IMF headers:

Message-ID: <CACQ76nh2VDypuwm1aHc1-s8ZmmyXg8XEosS6af6yurkVdT+8QQ@mail.gmail.com>

Message-Id: <208E8372-A9D9-468A-9B4B-BD97ED28F64C@garriss.org>

Notice the difference: 

    Message-ID:

    vs

    Message-Id:

Per the RFC, only the first is legal, but both are used in practice, and we’d like to allow either.  In our DFDL schema, “Message-ID” is an initiator, but suddenly we have two alternate initiators for the same element.

How we model this in DFDL?

TIA