Basic concepts of virtual (or merged) newsgroups.
By Clifford A. Adams
Last updated: June 27, 1993

	A virtual newsgroup (vgr) is a collection of articles from one
or more USENET newsgroups.  This collection can be created in two
major ways.  The first way is to simply use all the articles from a
set of existing newsgroups--the result is a "merged" newsgroup.  The
other, more exciting method is to take arbitrary articles from any
newsgroup(s)--this is what is usually meant by a "virtual" newsgroup.

	A vgr is specified by a set of commands in a file.  Here are a
couple simple vgrs:

----- cut -----
#This is a merged group with articles from rec.humor and rec.humor.funny
begin virtual
+rec.humor.funny
+rec.humor
end virtual
----- cut -----

----- cut -----
#This virtual group has only three articles
begin virtual
group comp.lang.c
+<435462@foo.bar.edu>
+<aaewbn32b2INN2gf@ick.acme.com>
group alt.folklore.computers
+<9532567@old.usenet.home>
#The "end virtual" command is optional at the end of a file
----- cut -----

	These vgr files are accessed through the group scan mode.  The
syntax is similar to a scan group file.  The difference is that the
virtual groups use an '@' character at the beginning of the filename.
Here are a few examples:

#These lines belong in a group scan file.
"Programming languages" @:program
"Best of rec.humor" @%p/scangroups/virt/besthumor
"Mary's selections from sci.physics" @/users/mary/News/vgr/selphysics

[More here later... on to the real documentation.]

	See the examples in the sample scangroups files under the
"merge" and "virt" directories.
