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 may 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 may
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