RFC 1494 (rfc1494) - Page 3 of 19

Equivalences between 1988 X

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.




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