+@code{nnfolder-directory}. This only works if you use long file names,
+though.
+
+@node Comparing Mail Backends
+@subsubsection Comparing Mail Backends
+
+First, just for terminology, the @dfn{backend} is the common word for a
+low-level access method---a transport, if you will, by which something
+is acquired. The sense is that one's mail has to come from somewhere,
+and so selection of a suitable backend is required in order to get that
+mail within spitting distance of Gnus.
+
+The same concept exists for Usenet itself: Though access to articles is
+typically done by NNTP these days, once upon a midnight dreary, everyone
+in the world got at Usenet by running a reader on the machine where the
+articles lay (the machine which today we call an NNTP server), and
+access was by the reader stepping into the articles' directory spool
+area directly. One can still select between either the @code{nntp} or
+@code{nnspool} backends, to select between these methods, if one happens
+actually to live on the server (or can see its spool directly, anyway,
+via NFS).
+
+The goal in selecting a mail backend is to pick one which
+simultaneously represents a suitable way of dealing with the original
+format plus leaving mail in a form that is convenient to use in the
+future. Here are some high and low points on each:
+
+@table @code
+@item nnmbox
+
+UNIX systems have historically had a single, very common, and well-
+defined format. All messages arrive in a single @dfn{spool file}, and
+they are delineated by a line whose regular expression matches
+@samp{^From_}. (My notational use of @samp{_} is to indicate a space,
+to make it clear in this instance that this is not the RFC-specified
+@samp{From:} header.) Because Emacs and therefore Gnus emanate
+historically from the Unix environment, it is simplest if one does not
+mess a great deal with the original mailbox format, so if one chooses
+this backend, Gnus' primary activity in getting mail from the real spool
+area to Gnus' preferred directory is simply to copy it, with no
+(appreciable) format change in the process. It is the ``dumbest'' way
+to move mail into availability in the Gnus environment. This makes it
+fast to move into place, but slow to parse, when Gnus has to look at
+what's where.
+
+@item nnbabyl
+
+Once upon a time, there was the DEC-10 and DEC-20, running operating
+systems called TOPS and related things, and the usual (only?) mail
+reading environment was a thing called Babyl. I don't know what format
+was used for mail landing on the system, but Babyl had its own internal
+format to which mail was converted, primarily involving creating a
+spool-file-like entity with a scheme for inserting Babyl-specific
+headers and status bits above the top of each message in the file.
+RMAIL was Emacs' first mail reader, it was written by Richard Stallman,
+and Stallman came out of that TOPS/Babyl environment, so he wrote RMAIL
+to understand the mail files folks already had in existence. Gnus (and
+VM, for that matter) continue to support this format because it's
+perceived as having some good qualities in those mailer-specific
+headers/status bits stuff. RMAIL itself still exists as well, of
+course, and is still maintained by Stallman.
+
+Both of the above forms leave your mail in a single file on your
+filesystem, and they must parse that entire file each time you take a
+look at your mail.
+
+@item nnml
+
+@code{nnml} is the backend which smells the most as though you were
+actually operating with an @code{nnspool}-accessed Usenet system. (In
+fact, I believe @code{nnml} actually derived from @code{nnspool} code,
+lo these years ago.) One's mail is taken from the original spool file,
+and is then cut up into individual message files, 1:1. It maintains a
+Usenet-style active file (analogous to what one finds in an INN- or
+CNews-based news system in (for instance) @file{/var/lib/news/active},
+or what is returned via the @samp{NNTP LIST} verb) and also creates
+@dfn{overview} files for efficient group entry, as has been defined for
+@sc{nntp} servers for some years now. It is slower in mail-splitting,
+due to the creation of lots of files, updates to the @code{nnml} active
+file, and additions to overview files on a per-message basis, but it is
+extremely fast on access because of what amounts to the indexing support
+provided by the active file and overviews.
+
+@code{nnml} costs @dfn{inodes} in a big way; that is, it soaks up the
+resource which defines available places in the filesystem to put new
+files. Sysadmins take a dim view of heavy inode occupation within
+tight, shared filesystems. But if you live on a personal machine where
+the filesystem is your own and space is not at a premium, @code{nnml}
+wins big.
+
+It is also problematic using this backend if you are living in a
+FAT16-based Windows world, since much space will be wasted on all these
+tiny files.
+
+@item nnmh
+
+The Rand MH mail-reading system has been around UNIX systems for a very
+long time; it operates by splitting one's spool file of messages into
+individual files, but with little or no indexing support -- @code{nnmh}
+is considered to be semantically equivalent to ``@code{nnml} without
+active file or overviews''. This is arguably the worst choice, because
+one gets the slowness of individual file creation married to the
+slowness of access parsing when learning what's new in one's groups.
+
+@item nnfolder
+
+Basically the effect of @code{nnfolder} is @code{nnmbox} (the first
+method described above) on a per-group basis. That is, @code{nnmbox}
+itself puts *all* one's mail in one file; @code{nnfolder} provides a
+little bit of optimization to this so that each of one's mail groups has
+a Unix mail box file. It's faster than @code{nnmbox} because each group
+can be parsed separately, and still provides the simple Unix mail box
+format requiring minimal effort in moving the mail around. In addition,
+it maintains an ``active'' file making it much faster for Gnus to figure
+out how many messages there are in each separate group.
+
+If you have groups that are expected to have a massive amount of
+messages, @code{nnfolder} is not the best choice, but if you receive
+only a moderate amount of mail, @code{nnfolder} is probably the most
+friendly mail backend all over.
+
+@end table
+
+
+@node Browsing the Web
+@section Browsing the Web
+@cindex web
+@cindex browsing the web
+@cindex www
+@cindex http
+
+Web-based discussion forums are getting more and more popular. On many
+subjects, the web-based forums have become the most important forums,
+eclipsing the importance of mailing lists and news groups. The reason
+is easy to understand---they are friendly to new users; you just point
+and click, and there's the discussion. With mailing lists, you have to
+go through a cumbersome subscription procedure, and most people don't
+even know what a news group is.
+
+The problem with this scenario is that web browsers are not very good at
+being newsreaders. They do not keep track of what articles you've read;
+they do not allow you to score on subjects you're interested in; they do
+not allow off-line browsing; they require you to click around and drive
+you mad in the end.
+
+So---if web browsers suck at reading discussion forums, why not use Gnus
+to do it instead?
+
+Gnus has been getting quite a collection of backends for providing
+interfaces to these sources.
+
+@menu
+* Web Searches:: Creating groups from articles that match a string.
+* Slashdot:: Reading the Slashdot comments.
+* Ultimate:: The Ultimate Bulletin Board systems.
+@end menu
+
+The main caveat with all these web sources is that they probably won't
+work for a very long time. Gleaning information from the @sc{html} data
+is guesswork at best, and when the layout is altered, the Gnus backend
+will fail. If you have reasonably new versions of these backends,
+though, you should be ok.
+
+One thing all these Web methods have in common is that the Web sources
+are often down, unavailable or just plain too slow to be fun. In those
+cases, it makes a lot of sense to let the Gnus Agent (@pxref{Gnus
+Unplugged}) handle downloading articles, and then you can read them at
+leisure from your local disk. No more World Wide Wait for you.
+
+
+@node Web Searches
+@subsection Web Searches
+@cindex nnweb
+@cindex DejaNews
+@cindex Alta Vista
+@cindex InReference
+@cindex Usenet searches
+@cindex searching the Usenet
+
+It's, like, too neat to search the Usenet for articles that match a
+string, but it, like, totally @emph{sucks}, like, totally, to use one of
+those, like, Web browsers, and you, like, have to, rilly, like, look at
+the commercials, so, like, with Gnus you can do @emph{rad}, rilly,
+searches without having to use a browser.
+
+The @code{nnweb} backend allows an easy interface to the mighty search
+engine. You create an @code{nnweb} group, enter a search pattern, and
+then enter the group and read the articles like you would any normal
+group. The @kbd{G w} command in the group buffer (@pxref{Foreign
+Groups}) will do this in an easy-to-use fashion.
+
+@code{nnweb} groups don't really lend themselves to being solid
+groups---they have a very fleeting idea of article numbers. In fact,
+each time you enter an @code{nnweb} group (not even changing the search
+pattern), you are likely to get the articles ordered in a different
+manner. Not even using duplicate suppression (@pxref{Duplicate
+Suppression}) will help, since @code{nnweb} doesn't even know the
+@code{Message-ID} of the articles before reading them using some search
+engines (DejaNews, for instance). The only possible way to keep track
+of which articles you've read is by scoring on the @code{Date}
+header---mark all articles posted before the last date you read the
+group as read.
+
+If the search engine changes its output substantially, @code{nnweb}
+won't be able to parse it and will fail. One could hardly fault the Web
+providers if they were to do this---their @emph{raison d'être} is to
+make money off of advertisements, not to provide services to the
+community. Since @code{nnweb} washes the ads off all the articles, one
+might think that the providers might be somewhat miffed. We'll see.
+
+You must have the @code{url} and @code{w3} package installed to be able
+to use @code{nnweb}.
+
+Virtual server variables:
+
+@table @code
+@item nnweb-type
+@vindex nnweb-type
+What search engine type is being used. The currently supported types
+are @code{dejanews}, @code{dejanewsold}, @code{altavista} and
+@code{reference}.
+
+@item nnweb-search
+@vindex nnweb-search
+The search string to feed to the search engine.
+
+@item nnweb-max-hits
+@vindex nnweb-max-hits
+Advisory maximum number of hits per search to display. The default is
+100.
+
+@item nnweb-type-definition
+@vindex nnweb-type-definition
+Type-to-definition alist. This alist says what @code{nnweb} should do
+with the various search engine types. The following elements must be
+present:
+
+@table @code
+@item article
+Function to decode the article and provide something that Gnus
+understands.
+
+@item map
+Function to create an article number to message header and URL alist.
+
+@item search
+Function to send the search string to the search engine.
+
+@item address
+The address the aforementioned function should send the search string
+to.
+
+@item id
+Format string URL to fetch an article by @code{Message-ID}.
+@end table
+
+@end table
+
+
+@node Slashdot
+@subsection Slashdot
+@cindex Slashdot
+@cindex nnslashdot
+
+Slashdot (@file{http://slashdot.org/}) is a popular news site, with
+lively discussion following the news articles. @code{nnslashdot} will
+let you read this forum in a convenient manner.
+
+The easiest way to read this source is to put something like the
+following in your @file{.gnus.el} file:
+
+@lisp
+(setq gnus-secondary-select-methods
+ '((nnslashdot "")))
+@end lisp
+
+This will make Gnus query the @code{nnslashdot} backend for new comments
+and groups. The @kbd{F} command will subscribe each new news article as
+a new Gnus group, and you can read the comments by entering these
+groups. (Note that the default subscription method is to subscribe new
+groups as zombies. Other methods are available (@pxref{Subscription
+Methods}).
+
+The following variables can be altered to change its behavior:
+
+@table @code
+@item nnslashdot-threaded
+Whether @code{nnslashdot} should display threaded groups or not. The
+default is @code{t}. To be able to display threads, @code{nnslashdot}
+has to retrieve absolutely all comments in a group upon entry. If a
+threaded display is not required, @code{nnslashdot} will only retrieve
+the comments that are actually wanted by the user. Threading is nicer,
+but much, much slower than untreaded.
+
+@item nnslashdot-directory
+@vindex nnslashdot-directory
+Where @code{nnslashdot} will store its files. The default value is
+@samp{~/News/slashdot/}.
+
+@item nnslashdot-active-url
+@vindex nnslashdot-active-url
+The @sc{url} format string that will be used to fetch the information on
+news articles and comments. The default is
+@samp{http://slashdot.org/search.pl?section=&min=%d}.
+
+@item nnslashdot-comments-url
+@vindex nnslashdot-comments-url
+The @sc{url} format string that will be used to fetch comments. The
+default is
+@samp{http://slashdot.org/comments.pl?sid=%s&threshold=%d&commentsort=%d&mode=flat&startat=%d}.
+
+@item nnslashdot-article-url
+@vindex nnslashdot-article-url
+The @sc{url} format string that will be used to fetch the news article. The
+default is
+@samp{http://slashdot.org/article.pl?sid=%s&mode=nocomment}.
+
+@item nnslashdot-threshold
+@vindex nnslashdot-threshold
+The score threshold. The default is -1.
+
+@item nnslashdot-group-number
+@vindex nnslashdot-group-number
+The number of old groups, in addition to the ten latest, to keep
+updated. The default is 0.
+
+@end table
+
+
+
+@node Ultimate
+@subsection Ultimate
+@cindex nnultimate
+@cindex Ultimate Bulletin Board
+
+The Ultimate Bulletin Board (@file{http://www.ultimatebb.com/}) is
+probably the most popular Web bulletin board system used. It has a
+quite regular and nice interface, and it's possible to get the
+information Gnus needs to keep groups updated.
+
+The easiest way to get started with @code{nnultimate} is to say
+something like the following in the group buffer: @kbd{B nnultimate RET
+http://www.tcj.com/messboard/ubbcgi/ RET}. (Substitute the @sc{url}
+(not including @samp{Ultimate.cgi} or the like at the end) for a forum
+you're interested in; there's quite a list of them on the Ultimate web
+site.) Then subscribe to the groups you're interested in from the
+server buffer, and read them from the group buffer.
+
+The following @code{nnultimate} variables can be altered:
+
+@table @code
+@item nnultimate-directory
+@vindex nnultimate-directory
+The directory where @code{nnultimate} stores its files. The default is
+@samp{~/News/ultimate/}.
+@end table