IDG stands for "Internet Discussion Group," a package written to support a
discussion list for the California Department of Transportation.  Its most
outstanding feature is that it requires only a single address, so that it can
run from a single, "normal" account.  IDG commands are sent in the subject
line of a message; if the system decides any given message is not a command,
it forwards it to the list.  This can be seen as an advantage, in that list
subscribers need remember only a single address; it also can be seen as a
disadvantage in that many subscribers are going to mis-form or mis-spell
their commands, thus causing IDG to send bogus messages to the list.

IDG is feature-rich, though probably not suitable for large lists.  Besides
"subscribe" and "unsubscribe," it supports "get," "put," and "rm" by general
users (maintaining knowledge of which subscriber "owns" each file, for
purposes of allowing and disallowing its deletion or change -- though IDG's
subscriber authentication is pretty low security), as well as "grep" for
searching the database of files.  It offers daily-digest-format delivery.  It
also supports two functions that, to my knowledge, are unique among MLM's.
With "filter" (similar to the LISTSERV "set topics" command, but more general
purpose), each subscriber can define a list of keywords which IDG will then
use to determine which messages should be forwarded to him or her -- that is,
if one of the subscriber's "filter" keywords is found in a new message's
header or body, IDG will send it to that subscriber; if it isn't, IDG won't.
(This function, while probably very useful, would be a resource hog on big
lists: it requires greping each message once for every subscriber who has a
filter set.)  IDG also offers a simple, built-in vote management function:
once the list administrator initializes a voting session, subscribers use the
"vote" command to cast their ballots "yes" or "no."  IDG tallies the votes as
it receives them, returning to each voter the status of the vote to date.

To try out IDG, send mail to <dot%t3ew@dot.ca.gov> with a subject line of
"help".  To get a copy of the software itself, send mail to
<ftpmail%t3ew@dot.ca.gov> with no subject and a message body of:
  connect
  get software/internet/idg
  quit 
If you have specific questions, you may want to write directly to IDG's
author, Don Stone <dstone%trmx2@dot.ca.gov>.