RFC 1494 (rfc1494) - Page 3 of 19
Equivalences between 1988 X
Alternative Format: Original Text Document
RFC 1494 X.400/MIME Body Equivalences August 1993
Comments (optional)
This section gives any additional commentary that might be
useful in understanding the mapping between the X.400 and MIME
representations.
The initial Equivalence Table entries in this document are described
using this convention. Any future submissions to the IANA should
follow this format.
3. Generic conversions
3.1. Byte copy
This is the trivial case, that is, no conversion at all. The byte
stream is simply copied between MIME and X.400.
This is the preferred conversion, since it is the simplest.
Implementors and vendors will be registering OBJECT IDENTIFIERs and
MIME content-types for their various objects. They are STRONGLY
ENCOURAGED to specify their content formats such that a gateway can
use Byte Copy to map between them.
Note that in some cases, it is necessary to define exactly which
ASN.1 construct to replace with the content of the MIME object.
3.2. Text Conversion
This type of conversion applies to text objects that cannot be mapped
using a simple Byte Copy. Conversion involves scanning and
reformatting the object. For example, the MIME and X.400 objects
might differ in their encoding of nonstandard characters, or line or
page breaks.
3.3. Image Conversion
This conversion type applies to raster images, like Group 3 Facsimile
or JPEG. Again, it differs from Byte Copy in that it involves
scanning reformatting the byte stream. It differs from Text
Conversion in that it is pixel- oriented, rather than character-
oriented.
3.4. Tunneling
This is not a conversion at all, but an encapsulation of the object.
This is the fallback conversion, used when no explicit mapping
applies.
Alvestrand & Thompson