One very basic mapping table in PMDF is the character set conversion table. The name of this table is CHARSET-CONVERSION. It is used to specify what sorts of channel-to-channel character set conversions, labelling conversions, and message reformatting should be done.

On many systems there is no need to do character set conversions or message reformating and therefore this table is not needed. Situations arise, however, where character conversions must be done. For example, sites running Japanese OpenVMS may need to convert between DEC Kanji and the ISO-2022 Kanji currently used on the Internet. Another possible use of conversions arises when multinational characters are so heavily used that the slight discrepancies between the DEC Multinational Character Set (DEC-MCS) and the ISO-8859-1 character set specified for use in MIME may become an issue, and actual conversion between the two may therefore be needed.

The CHARSET-CONVERSION mapping can also be used to alter the format of messages. Facilities are provided to convert a number of non-MIME formats into MIME. Changes to MIME encodings and structure are also possible. These options are used when messages are being relayed to systems that only support MIME or some subset of MIME. And finally, conversion from MIME into non-MIME formats is provided in a small number of cases.

PMDF will probe the CHARSET-CONVERSION mapping table in two different ways. The first probe is used to determine whether or not PMDF should reformat the message and if so, what formatting options should be used. (If no reformatting is specified PMDF does not bother to check for specific character set conversions.) The input string for this first probe has the general form:

IN-CHAN=in-channel;OUT-CHAN=out-channel;CONVERT

Here in-channel is the name of the source channel (where the message comes from) and out-channel is the name of the destination channel (where the message is going). If a match occurs the resulting string should be a comma-separated list of keywords. Table 6-1 lists the available keywords.

Table 6-1 CHARSET-CONVERSIONS Mapping Table Keywords

Keyword	Action
Always	Force conversion even when conversion channel is an intermediate destination
Appledouble	Convert other MacMIME formats to Appledouble format
Applesingle	Convert other MacMIME formats to Applesingle format
BASE64	Switch MIME encodings to BASE64
Binhex	Convert other MacMIME formats, or parts including Macintosh type and Mac creator information, to Binhex format
Block	Extract just the data fork from MacMIME format parts
Bottom	"Flatten" any message/rfc822 body part (forwarded message) into a message content part and a header part
Delete	"Flatten" any message/rfc822 body part (forwarded message) into a message content part, deleting the forwarded headers
Level	Remove redundant multipart levels from message
Macbinary	Convert other MacMIME formats, or parts including Macintosh type and Macintosh creator information, to Macbinary format
No	Disable conversion
Pathworks	Convert message to Pathworks Mail format
QUOTED-PRINTABLE	Switch MIME encodings to QUOTED-PRINTABLE
Record,Text	Line wrap text/plain parts at 80 characters
Record,Text= n	Line wrap text/plain parts at n characters
RFC1154	Convert message to RFC 1154 format
Top	"Flatten" any message/rfc822 body part (forwarded message) into a header part and a message content part
UUENCODE	Switch MIME encodings to X-UUENCODE
Yes	Enable conversion

A No is assumed if no match occurs.