PMDF System Manager's Guide
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39.2.6 Attachment Handling: Content Type and Encoding Mappings

Message Router's DECBODY7 binary file attachments can contain a special tag string that identifies the type of attachment. These strings are roughly equivalent to and thus can be translated to and from MIME content types. These optional conversions are implemented using a set of mapping tables in the mapping file, used by both the MR and MRIF channels. The following sections describe all the mappings used by the Message Router channels relating to such attachments. Examples of these mappings are also provided in the file mr_mappings.sample located in the PMDF table directory.

Note that the tags used on the Message Router side are site configurable, and indeed in the case of TeamLinks user configurable. Sites should expect to need to modify the sample mapping tables to correspond to the types of Message Router tags actually in use at their site.

Note also that Message Router also has other sorts of parts, other sorts of DECBODY parts, to which the discussion of this section is not applicable. For instance, older versions of Message Router can convey WordPerfect documents in special WordPerfect DECBODY1 parts, rather than using DECBODY7 parts as more recent versions do; see the CONVERT_WPCORP option in Section 39.2.5.2 for a discussion of PMDF-MR's handling of such DECBODY1 parts. Another example is that plain text attachments are not normally stored in Message Router DECBODY7 parts, but rather are stored in text Message Router attachments automatically; thus normally no mapping entries need (or should) be set up for plain text parts.

39.2.6.1 MIME-TO-MR-CONTENT-TYPES Mapping

The MIME-TO-MR-CONTENT-TYPES mapping table maps MIME content type and subtype information into Message Router tags and FDL information for Message Router DECBODY7 parts. Input to the mapping consists of a MIME content type/subtype specification. The output of the mapping consists of a Message Router tag optionally followed by a semicolon and an FDL specification. A minimal MIME-TO-MR-CONTENT-TYPES mapping would be: 


MIME-TO-MR-CONTENT-TYPES 
 
  APPLICATION/DDIF                DDIF 
  APPLICATION/POSTSCRIPT          PS 
  IMAGE/GIF                       GIF 
  IMAGE/TIFF                      TIFF

39.2.6.2 MR-TO-MIME-CONTENT-TYPES Mapping

The MR-TO-MIME-CONTENT-TYPES mapping table maps Message Router tags on Message Router DECBODY7 parts into MIME content type and subtype information. A minimal MR-TO-MIME-CONTENT-TYPES mapping would be: 


MR-TO-MIME-CONTENT-TYPES 
 
  DDIF                            APPLICATION/DDIF 
  PS                              APPLICATION/POSTSCRIPT 
  GIF                             IMAGE/GIF 
  TIFF                            IMAGE/TIFF

39.2.6.3 MR-TO-MIME-ENCODINGS Mapping

The MR-TO-MIME-ENCODINGS mapping table maps Message Router tags on DECBODY7 parts into MIME transfer encoding information. The specified encoding will be used to encode the corresponding attachment data. If no encoding is specified the default encoding for the channel will be used; since the default usually provides reasonable behavior, this mapping table is not usually needed. A sample MR-TO-MIME-ENCODINGS mapping would be: 


MR-TO-MIME-ENCODINGS 
 
  DDIF                            BASE64 
  PS                              QUOTED-PRINTABLE 
  GIF                             BASE64 
  TIFF                            BASE64

39.2.6.4 MR-TO-FILENAME Mapping

Message Router does not itself transmit filename information for attachments. (Though see the A1_COMPAT_MODE option in Section 39.2.5.2 for a discussion of a special ALL-IN-1 technique used by ALL-IN-1 to work around this Message Router restriction.) When it is necessary to reconstruct some sort of filename, then the MR-TO-FILENAME mapping can be used to regenerate filenames based on the Message Router tag information on Message Router DECBODY7 parts. Note that this facility cannot be used to guarantee preservation of the original filename, since any original filename information was lost in the transit through Message Router. However, careful correlation of MR type tags with common filename usage will help in some environments to restore functionality otherwise lost. (Note that the MIME content type and subtype labelling is the more general way of labelling attachments in a true MIME environment; adding a filename as well is purely secondary.)

A minimal MR-TO-FILENAME mapping would be: 


MR-TO-FILENAME 
 
  DDIF                            DDIF.DIF 
  GIF                             GIF.GIF 
  PS                              PS.PS 
  TIFF                            TIFF.TIF

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