RFC 1495 (rfc1495) - Page 3 of 11
Mapping between X
Alternative Format: Original Text Document
RFC 1495 MHS/RFC-822 Message Body Mapping August 1993
through an MHS relay); and,
(3) Allow MHS body parts to "tunnel" through a MIME relay that is,
two MHS users can exchange body parts without loss through a MIME
relay).
Other, related, scenarios can also be easily accommodated.
To facilitate the mapping process, the Internet Assigned Numbers
Authority (IANA) maintains a table termed the "IANA MHS/MIME
Equivalence Table". Once an enterprise has registered an OID to
describe an MHS body part, it should complete a corresponding
registry with the IANA for a MIME content-type/subtype. In practice,
the corresponding content-type will be "application", with an
appropriate choice of sub-type and possible parameters. If a new
MIME content-type/subtype is registered with the IANA without a
corresponding entry in the Equivalence Table, the IANA will assign it
an OID, from the arc defined in this memo. See [4], section 5 for
details.
The companion document, "Equivalences between 1988 X.400 and RFC-822
Message Bodies"[4], defines the initial configuration of this table.
The mappings described in both this document and the companion
document use the notational conventions of RFC-1327.
3. Mapping between X.400 and RFC-822 Message Bodies
MHS messages are comprised of an IPMS.heading and an IPMS.body. The
IPMS.Body is a sequence of IPMS.BodyParts. An IPMS.BodyPart may be a
nested message (IPMS.MessageBodyPart).
A MIME message consists of headers and a content. For the purpose of
discussion, the content may be structured (multipart or message), or
atomic (otherwise). An element of a structured content may be a
message or a content. Both message and structured content have
subtypes which do not have direct analogies in MHS.
The mapping between X.400 and RFC-822 message bodies which this
document defines is symmetrical for the following cases:
(1) any atomic body part
(2) multipart: digest and mixed subtypes
(3) message/rfc822
RFC-1327 specifies the mappings for headers. Section 4 describes how
those mappings are modified by this document. When mapping between
Alvestrand, Kille, Miles, Rose & Thompson