Re: yet another way to indicate related MIME body parts

> SGML has a packaging scheme too, SDIF.  Don't know if anyone uses it.
SDIF is used.  In some communities, it is used quite heavily.  In most
other communities that have to exchange documents, DTDs, and public
types, it is considered far too general, complex, and overhead-laden for
the applications usually encountered, and simple, problem-specific
arrangements are used instead.

There may be some analogies here, but I will leave them to others.
    john