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# Scoring

Other people use kill files, but we here at Gnus Towers like scoring better than killing, so we'd rather switch than fight. They do something completely different as well, so sit up straight and pay attention!

All articles have a default score (`gnus-summary-default-score`), which is 0 by default. This score may be raised or lowered either interactively or by score files. Articles that have a score lower than `gnus-summary-mark-below` are marked as read.

Gnus will read any score files that apply to the current group before generating the summary buffer.

There are several commands in the summary buffer that insert score entries based on the current article. You can, for instance, ask Gnus to lower or increase the score of all articles with a certain subject.

There are two sorts of scoring entries: Permanent and temporary. Temporary score entries are self-expiring entries. Any entries that are temporary and have not been used for, say, a week, will be removed silently to help keep the sizes of the score files down.

- Summary Score Commands: Adding score entries for the current group.
- Group Score Commands: General score commands.
- Score Variables: Customize your scoring. (My, what terminology).
- Score File Format: What a score file may contain.
- Score File Editing: You can edit score files by hand as well.
- Adaptive Scoring: Big Sister Gnus *knows* what you read.
- Followups To Yourself: Having Gnus notice when people answer you.
- Scoring Tips: How to score effectively.
- Reverse Scoring: That problem child of old is not problem.
- Global Score Files: Earth-spanning, ear-splitting score files.
- Kill Files: They are still here, but they can be ignored.
- GroupLens: Getting predictions on what you like to read.

## Summary Score Commands

The score commands that alter score entries do not actually modify real score files. That would be too inefficient. Gnus maintains a cache of previously loaded score files, one of which is considered the current score file alist. The score commands simply insert entries into this list, and upon group exit, this list is saved.

The current score file is by default the group's local score file, even if no such score file actually exists. To insert score commands into some other score file (eg. ``all.SCORE'`), you must first make this score file the current one.

General score commands that don't actually change the score file:

`V s`
  Set the score of the current article (`gnus-summary-set-score`).
`V S`
  Display the score of the current article (`gnus-summary-current-score`).
`V t`
  Display all score rules that have been used on the current article (`gnus-score-find-trace`).
`V R`
  Run the current summary through the scoring process (`gnus-summary-rescore`). This might be useful if you're playing around with your score files behind Gnus' back and want to see the effect you're having.
`V a`
  Add a new score entry, and allow specifying all elements (`gnus-summary-score-entry`).
`V c`
  Make a different score file the current (`gnus-score-change-score-file`).
`V e`
  Edit the current score file (`gnus-score-edit-current-scores`). You will be popped into a `gnus-score-mode` buffer (see section Score File Editing).
`V f`
  Edit a score file and make this score file the current one (`gnus-score-edit-file`).
`V F`
  Flush the score cahe (`gnus-score-flush-cache`). This is useful after editing score files.
`V C`
  Customize a score file in a visually pleasing manner (`gnus-score-customize`).
`I C-i`
  Increase the score of the current article (`gnus-summary-raise-score`).
`L C-l`
  Lower the score of the current article (`gnus-summary-lower-score`).

The rest of these commands modify the local score file.

`V m`
  Prompt for a score, and mark all articles with a score below this as read (`gnus-score-set-mark-below`).
`V E`
  Expunge all articles with a score below the default score (or the numeric prefix) (`gnus-score-set-expunge-below`).

The keystrokes for actually making score entries follow a very regular pattern, so there's no need to list all the commands. (Hundreds of them.)

1. The first key is either `I` (upper case i) for increasing the score or `L` for lowering the score.
2. The second key says what header you want to score on. The following keys are available:
   `a`
     Score on the author name.
   `s`
     Score on the subject line.
   `x`
     Score on the Xref line--i.e., the cross-posting line.
   `t`
     Score on thread--the References line.
   `d`
     Score on the date.
   `l`
     Score on the number of lines.
   `i`
     Score on the Message-ID.
   `f`
     Score on followups.
   `b`
     Score on the body.
   `h`
     Score on the head.
3. The third key is the match type. Which match types are legal depends on what headers you are scoring on.
   `strings`
     `e`
       Exact matching.
     `s`
       Substring matching.
     `f`
       Fuzzy matching.
     `r`
       Regexp matching
   `date`
     `b`
       Before date.
     `a`
       At date.
     `n`
       This date.
   `number`
     `<`
       Less than number.
     `=`
       Equal to number.
     `>`
       Greater than number.
4. The fourth and final key says whether this is a temporary (i.e., expiring) score entry, or a permanent (i.e., non-expiring) score entry, or whether it is to be done immediately, without adding to the score file.
   `t`
     Temporary score entry.
   `p`
     Permanent score entry.
   `i`
     Immediately scoring.

So, let's say you want to increase the score on the current author with exact matching permanently: `I a e p`. If you want to lower the score based on the subject line, using substring matching, and make a temporary score entry: `L s s t`. Pretty easy.

To make things a bit more complicated, there are shortcuts. If you use a capital letter on either the second or third keys, Gnus will use defaults for the remaining one or two keystrokes. The defaults are "substring" and "temporary". So `I A` is the same as `I a s t`, and `I a R` is the same as `I a r t`.

The `gnus-score-mimic-keymap` says whether these commands will pretend they are keymaps or not.

## Group Score Commands

There aren't many of these as yet, I'm afraid.

`W f`
  Gnus maintains a cache of score alists to avoid having to reload them all the time. This command will flush the cache (`gnus-score-flush-cache`).

## Score Variables

`gnus-use-scoring`
  If `nil`, Gnus will not check for score files, and will not, in general, do any score-related work. This is `t` by default.
`gnus-kill-killed`
  If this variable is `nil`, Gnus will never apply score files to articles that have already been through the kill process. While this may save you lots of time, it also means that if you apply a kill file to a group, and then change the kill file and want to run it over you group again to kill more articles, it won't work. You have to set this variable to `t` to do that. (It is `t` by default.)
`gnus-kill-files-directory`
  All kill and score files will be stored in this directory, which is initialized from the `SAVEDIR` environment variable by default. This is ``~/News/'` by default.
`gnus-score-file-suffix`
  Suffix to add to the group name to arrive at the score file name (``SCORE'` by default.)
`gnus-score-uncacheable-files`
  All score files are normally cached to avoid excessive re-loading of score files. However, if this might make you Emacs grow big and bloated, so this regexp can be used to weed out score files that are unlikely to be needed again. It would be a bad idea to deny caching of ``all.SCORE'`, while it might be a good idea to not cache ``comp.infosystems.www.authoring.misc.ADAPT'`. In fact, this variable is ``ADAPT$'` by default, so no adaptive score files will be cached.
`gnus-save-score`
  If you have really complicated score files, and do lots of batch scoring, then you might set this variable to `t`. This will make Gnus save the scores into the ``.newsrc.eld'` file.
`gnus-score-interactive-default-score`
  Score used by all the interactive raise/lower commands to raise/lower score with. Default is 1000, which may seem excessive, but this is to ensure that the adaptive scoring scheme gets enough room to play with. We don't want the small changes from the adaptive scoring to overwrite manually entered data.
`gnus-summary-default-score`
  Default score of an article, which is 0 by default.
`gnus-score-over-mark`
  Mark (in the third column) used for articles with a score over the default. Default is ``+'`.
`gnus-score-below-mark`
  Mark (in the third column) used for articles with a score below the default. Default is ``-'`.
`gnus-score-find-score-files-function`
  Function used to find score files for the current group. This function is called with the name of the group as the argument. Predefined functions available are:
  `gnus-score-find-single`
    Only apply the group's own score file.
  `gnus-score-find-bnews`
    Apply all score files that match, using bnews syntax. This is the default. For instance, if the current group is ``gnu.emacs.gnus'`, ``all.emacs.all.SCORE'`, ``not.alt.all.SCORE'` and ``gnu.all.SCORE'` would all apply. In short, the instances of ``all'` in the score file names are translated into ``.*'`, and then a regexp match is done. This means that if you have some score entries that you want to apply to all groups, then you put those entries in the ``all.SCORE'` file.
  `gnus-score-find-hierarchical`
    Apply all score files from all the parent groups. This means that you can't have score files like ``all.SCORE'` or ``all.emacs.SCORE'`, but you can have ``SCORE'`, ``comp.SCORE'` and ``comp.emacs.SCORE'`.
  This variable can also be a list of functions. In that case, all these functions will be called, and all the returned lists of score files will be applied. These functions can also return lists of score alists directly. In that case, the functions that return these non-file score alists should probably be placed before the "real" score file functions, to ensure that the last score file returned is the local score file. Phu.
`gnus-score-expiry-days`
  This variable says how many days should pass before an unused score file entry is expired. If this variable is `nil`, no score file entries are expired. It's 7 by default.
`gnus-update-score-entry-dates`
  If this variable is non-`nil`, matching score entries will have their dates updated. (This is how Gnus controls expiry--all non-matching entries will become too old while matching entries will stay fresh and young.) However, if you set this variable to `nil`, even matching entries will grow old and will have to face that oh-so grim reaper.
`gnus-score-after-write-file-function`
  Function called with the name of the score file just written.

## Score File Format

A score file is an `emacs-lisp` file that normally contains just a single form. Casual users are not expected to edit these files; everything can be changed from the summary buffer.

Anyway, if you'd like to dig into it yourself, here's an example:

    (("from"
      ("Lars Ingebrigtsen" -10000)
      ("Per Abrahamsen")
      ("larsi\\|lmi" -50000 nil R))
     ("subject"
      ("Ding is Badd" nil 728373))
     ("xref"
      ("alt.politics" -1000 728372 s))
     ("lines"
      (2 -100 nil <))
     (mark 0)
     (expunge -1000)
     (mark-and-expunge -10)
     (read-only nil)
     (orphan -10)
     (adapt t)
     (files "/hom/larsi/News/gnu.SCORE")
     (exclude-files "all.SCORE")
     (local (gnus-newsgroup-auto-expire t)
            (gnus-summary-make-false-root 'empty))
     (eval (ding)))

This example demonstrates absolutely everything about a score file.

Even though this looks much like lisp code, nothing here is actually `eval`ed. The lisp reader is used to read this form, though, so it has to be legal syntactically, if not semantically.

Six keys are supported by this alist:

`STRING`
  If the key is a string, it is the name of the header to perform the match on. Scoring can only be performed on these eight headers: `From`, `Subject`, `References`, `Message-ID`, `Xref`, `Lines`, `Chars` and `Date`. In addition to these headers, there are three strings to tell Gnus to fetch the entire article and do the match on larger parts of the article: `Body` will perform the match on the body of the article, `Head` will perform the match on the head of the article, and `All` will perform the match on the entire article. Note that using any of these last three keys will slow down group entry considerably. The final "header" you can score on is `Followup`. These score entries will result in new score entries being added for all follow-ups to articles that matches these score entries. Following this key is a arbitrary number of score entries, where each score entry has one to four elements.
  1. The first element is the match element. On most headers this will be a string, but on the Lines and Chars headers, this must be an integer.
  2. If the second element is present, it should be a number--the score element. This number should be an integer in the neginf to posinf interval. This number is added to the score of the article if the match is successful. If this element is not present, the `gnus-score-interactive-default-score` number will be used instead. This is 1000 by default.
  3. If the third element is present, it should be a number--the date element. This date says when the last time this score entry matched, which provides a mechanism for expiring the score entries. It this element is not present, the score entry is permanent. The date is represented by the number of days since December 31, 1 ce.
  4. If the fourth element is present, it should be a symbol--the type element. This element specifies what function should be used to see whether this score entry matches the article. What match types that can be used depends on what header you wish to perform the match on.
     From, Subject, References, Xref, Message-ID
       For most header types, there are the `r` and `R` (regexp) as well as `s` and `S` (substring) types and `e` and `E` (exact match) types. If this element is not present, Gnus will assume that substring matching should be used. `R` and `S` differ from the other two in that the matches will be done in a case-sensitive manner. All these one-letter types are really just abbreviations for the `regexp`, `string` and `exact` types, which you can use instead, if you feel like.
     Lines, Chars
       These two headers use different match types: `<`, `>`, `=`, `>=` and `<=`.
     Date
       For the Date header we have three match types: `before`, `at` and `after`. I can't really imagine this ever being useful, but, like, it would feel kinda silly not to provide this function. Just in case. You never know. Better safe than sorry. Once burnt, twice shy. Don't judge a book by its cover. Never not have sex on a first date.
     Head, Body, All
       These three match keys use the same match types as the `From` (etc) header uses.
     Followup
       This match key will add a score entry on all articles that followup to some author. Uses the same match types as the `From` header uses.
     Thread
       This match key will add a score entry on all articles that are part of a thread. Uses the same match types as the `References` header uses.
`mark`
  The value of this entry should be a number. Any articles with a score lower than this number will be marked as read.
`expunge`
  The value of this entry should be a number. Any articles with a score lower than this number will be removed from the summary buffer.
`mark-and-expunge`
  The value of this entry should be a number. Any articles with a score lower than this number will be marked as read and removed from the summary buffer.
`thread-mark-and-expunge`
  The value of this entry should be a number. All articles that belong to a thread that has a total score below this number will be marked as read and removed from the summary buffer. `gnus-thread-score-function` says how to compute the total score for a thread.
`files`
  The value of this entry should be any number of file names. These files are assumed to be score files as well, and will be loaded the same way this one was.
`exclude-files`
  The clue of this entry should be any number of files. This files will not be loaded, even though they would normally be so, for some reason or other.
`eval`
  The value of this entry will be `eval`el. This element will be ignored when handling global score files.
`read-only`
  Read-only score files will not be updated or saved. Global score files should feature this atom (see section Global Score Files).
`orphan`
  The value of this entry should be a number. Articles that do not have parents will get this number added to their scores. Imagine you follow some high-volume newsgroup, like ``comp.lang.c'`. Most likely you will only follow a few of the threads, also want to see any new threads. You can do this with the following two score file entries:

      	(orphan -500)
      	(mark-and-expunge -100)

  When you enter the group the first time, you will only see the new threads. You then raise the score of the threads that you find interesting (with `I T` or `I S`), and ignore (`C y`) the rest. Next time you enter the group, you will see new articles in the interesting threads, plus any new threads. I.e. -- the orphan score atom is for high-volume groups where there exist a few interesting threads which can't be found automatically by ordinary scoring rules.
`adapt`
  This entry controls the adaptive scoring. If it is `t`, the default adaptive scoring rules will be used. If it is `ignore`, no adaptive scoring will be performed on this group. If it is a list, this list will be used as the adaptive scoring rules. If it isn't present, or is something other than `t` or `ignore`, the default adaptive scoring rules will be used. If you want to use adaptive scoring on most groups, you'd set `gnus-use-adaptive-scoring` to `t`, and insert an `(adapt ignore)` in the groups where you do not want adaptive scoring. If you only want adaptive scoring in a few groups, you'd set `gnus-use-adaptive-scoring` to `nil`, and insert `(adapt t)` in the score files of the groups where you want it.
`adapt-file`
  All adaptive score entries will go to the file named by this entry. It will also be applied when entering the group. This atom might be handy if you want to adapt on several groups at once, using the same adaptive file for a number of groups.
`local`
  The value of this entry should be a list of `(VAR VALUE)` pairs. Each var will be made buffer-local to the current summary buffer, and set to the value specified. This is a convenient, if somewhat strange, way of setting variables in some groups if you don't like hooks much.

## Score File Editing

You normally enter all scoring commands from the summary buffer, but you might feel the urge to edit them by hand as well, so we've supplied you with a mode for that.

It's simply a slightly customized `emacs-lisp` mode, with these additional commands:

`C-c C-c`
  Save the changes you have made and return to the summary buffer (`gnus-score-edit-done`).
`C-c C-d`
  Insert the current date in numerical format (`gnus-score-edit-insert-date`). This is really the day number, if you were wondering.
`C-c C-p`
  The adaptive score files are saved in an unformatted fashion. If you intend to read one of these files, you want to pretty print it first. This command (`gnus-score-pretty-print`) does that for you.

Type `M-x gnus-score-mode` to use this mode.

`gnus-score-menu-hook` is run in score mode buffers.

In the summary buffer you can use commands like `V f` and `V e` to begin editing score files.

## Adaptive Scoring

If all this scoring is getting you down, Gnus has a way of making it all happen automatically--as if by magic. Or rather, as if by artificial stupidity, to be precise.

When you read an article, or mark an article as read, or kill an article, you leave marks behind. On exit from the group, Gnus can sniff these marks and add score elements depending on what marks it finds. You turn on this ability by setting `gnus-use-adaptive-scoring` to `t`.

To give you complete control over the scoring process, you can customize the `gnus-default-adaptive-score-alist` variable. For instance, it might look something like this:

    (defvar gnus-default-adaptive-score-alist
      '((gnus-unread-mark)
        (gnus-ticked-mark (from 4))
        (gnus-dormant-mark (from 5))
        (gnus-del-mark (from -4) (subject -1))
        (gnus-read-mark (from 4) (subject 2))
        (gnus-expirable-mark (from -1) (subject -1))
        (gnus-killed-mark (from -1) (subject -3))
        (gnus-kill-file-mark)
        (gnus-ancient-mark)
        (gnus-low-score-mark)
        (gnus-catchup-mark (from -1) (subject -1))))

As you see, each element in this alist has a mark as a key (either a variable name or a "real" mark--a character). Following this key is a arbitrary number of header/score pairs. If there are no header/score pairs following the key, no adaptive scoring will be done on articles that have that key as the article mark. For instance, articles with `gnus-unread-mark` in the example above will not get adaptive score entries.

Each article can have only one mark, so just a single of these rules will be applied to each article.

To take `gnus-del-mark` as an example--this alist says that all articles that have that mark (i.e., are marked with ``D'`) will have a score entry added to lower based on the `From` header by -4, and lowered by `Subject` by -1. Change this to fit your prejudices.

If you have marked 10 articles with the same subject with `gnus-del-mark`, the rule for that mark will be applied ten times. That means that that subject will get a score of ten times -1, which should be, unless I'm much mistaken, -10.

The headers you can score on are `from`, `subject`, `message-id`, `references`, `xref`, `lines`, `chars` and `date`. In addition, you can score on `followup`, which will create an adaptive score entry that matches on the `References` header using the `Message-ID` of the current article, thereby matching the following thread.

You can also score on `thread`, which will try to score all articles that appear in a thread. `thread` matches uses a `Message-ID` to match on the `References` header of the article. If the match is made, the `Message-ID` of the article is added to the `thread` rule. (Think about it. I'd recommend two aspirins afterwards.)

If you use this scheme, you should set the score file atom `mark` to something small--like -300, perhaps, to avoid having small random changes result in articles getting marked as read.

After using adaptive scoring for a week or so, Gnus should start to become properly trained and enhance the authors you like best, and kill the authors you like least, without you having to say so explicitly.

You can control what groups the adaptive scoring is to be performed on by using the score files (see section Score File Format). This will also let you use different rules in different groups.

The adaptive score entries will be put into a file where the name is the group name with `gnus-adaptive-file-suffix` appended. The default is ``ADAPT'`.

When doing adaptive scoring, substring or fuzzy matching would probably give you the best results in most cases. However, if the header one matches is short, the possibility for false positives is great, so if the length of the match is less than `gnus-score-exact-adapt-limit`, exact matching will be used. If this variable is `nil`, exact matching will always be used to avoid this problem.

## Followups To Yourself

Gnus offers two commands for picking out the `Message-ID` header in the current buffer. Gnus will then add a score rule that scores using this `Message-ID` on the `References` header of other articles. This will, in effect, increase the score of all articles that respond to the article in the current buffer. Quite useful if you want to easily note when people answer what you've said.

`gnus-score-followup-article`
  This will add a score to articles that directly follow up your own article.
`gnus-score-followup-thread`
  This will add a score to all articles that appear in a thread "below" your own article.

These two functions are both primarily meant to be used in hooks like `gnus-inews-article-hook`.

## Scoring Tips

Crossposts
  If you want to lower the score of crossposts, the line to match on is the `Xref` header.

      ("xref" (" talk.politics.misc:" -1000))

Multiple crossposts
  If you want to lower the score of articles that have been crossposted to more than, say, 3 groups:

      ("xref" ("[^:\n]+:[0-9]+ +[^:\n]+:[0-9]+ +[^:\n]+:[0-9]+" -1000 nil r))

Matching on the body
  This is generally not a very good idea--it takes a very long time. Gnus actually has to fetch each individual article from the server. But you might want to anyway, I guess. Even though there are three match keys (`Head`, `Body` and `All`), you should choose one and stick with it in each score file. If you use any two, each article will be fetched twice. If you want to match a bit on the `Head` and a bit on the `Body`, just use `All` for all the matches.
Marking as read
  You will probably want to mark articles that has a score below a certain number as read. This is most easily achieved by putting the following in your ``all.SCORE'` file:

      ((mark -100))

  You may also consider doing something similar with `expunge`.
Negated character classes
  If you say stuff like `[^abcd]*`, you may get unexpected results. That will match newlines, which might lead to, well, The Unknown. Say `[^abcd\n]*` instead.

## Reverse Scoring

If you want to keep just articles that have ``Sex with Emacs'` in the subject header, and expunge all other articles, you could put something like this in your score file:

    (("subject"
      ("Sex with Emacs" 2))
     (mark 1)
     (expunge 1))

So, you raise all articles that match ``Sex with Emacs'` and mark the rest as read, and expunge them to boot.

## Global Score Files

Sure, other newsreaders have "global kill files". These are usually nothing more than a single kill file that applies to all groups, stored in the user's home directory. Bah! Puny, weak newsreaders!

What I'm talking about here are Global Score Files. Score files from all over the world, from users everywhere, uniting all nations in one big, happy score file union! Ange-score! New and untested!

All you have to do to use other people's score files is to set the `gnus-global-score-files` variable. One entry for each score file, or each score file directory. Gnus will decide by itself what score files are applicable to which group.

Say you want to use all score files in the ``/ftp@ftp.some-where:/pub/score'` directory and the single score file ``/ftp@ftp.ifi.uio.no:/pub/larsi/ding/score/soc.motss.SCORE'`:

    (setq gnus-global-score-files
          '("/ftp@ftp.ifi.uio.no:/pub/larsi/ding/score/soc.motss.SCORE"
            "/ftp@ftp.some-where:/pub/score/"))

Simple, eh? Directory names must end with a ``/'`. These directories are typically scanned only once during each Gnus session. If you feel the need to manually re-scan the remote directories, you can use the `gnus-score-search-global-directories` command.

Note that, at present, using this option will slow down group entry somewhat. (That is--a lot.)

If you want to start maintaining score files for other people to use, just put your score file up for anonymous ftp and announce it to the world. Become a retro-moderator! Participate in the retro-moderator wars sure to ensue, where retro-moderators battle it out for the sympathy of the people, luring them to use their score files on false premises! Yay! The net is saved!

Here are some tips for the would-be retro-moderator, off the top of my head:

- Articles that are heavily crossposted are probably junk.
- To lower a single inappropriate article, lower by `Message-ID`.
- Particularly brilliant authors can be raised on a permanent basis.
- Authors that repeatedly post off-charter for the group can safely be lowered out of existence.
- Set the `mark` and `expunge` atoms to obliterate the nastiest articles completely.
- Use expiring score entries to keep the size of the file down. You should probably have a long expiry period, though, as some sites keep old articles for a long time.

... I wonder whether other newsreaders will support global score files in the future. Snicker. Yup, any day now, newsreaders like Blue Wave, xrn and 1stReader are bound to implement scoring. Should we start holding our breath yet?

## Kill Files

Gnus still supports those pesky old kill files. In fact, the kill file entries can now be expiring, which is something I wrote before Daniel Quinlan thought of doing score files, so I've left the code in there.

In short, kill processing is a lot slower (and I do mean a lot) than score processing, so it might be a good idea to rewrite your kill files into score files.

Anyway, a kill file is a normal `emacs-lisp` file. You can put any forms into this file, which means that you can use kill files as some sort of primitive hook function to be run on group entry, even though that isn't a very good idea.

XCNormal kill files look like this:

    (gnus-kill "From" "Lars Ingebrigtsen")
    (gnus-kill "Subject" "ding")
    (gnus-expunge "X")

This will mark every article written by me as read, and remove them from the summary buffer. Very useful, you'll agree.

Other programs use a totally different kill file syntax. If Gnus encounters what looks like a `rn` kill file, it will take a stab at interpreting it.

Two summary functions for editing a GNUS kill file:

`M-k`
  Edit this group's kill file (`gnus-summary-edit-local-kill`).
`M-K`
  Edit the general kill file (`gnus-summary-edit-global-kill`).

Two group mode functions for editing the kill files:

`M-k`
  Edit this group's kill file (`gnus-group-edit-local-kill`).
`M-K`
  Edit the general kill file (`gnus-group-edit-global-kill`).

Kill file variables:

`gnus-kill-file-name`
  A kill file for the group ``soc.motss'` is normally called ``soc.motss.KILL'`. The suffix appended to the group name to get this file name is detailed by the `gnus-kill-file-name` variable. The "global" kill file (not in the score file sense of "global", of course) is called just ``KILL'`.
`gnus-kill-save-kill-file`
  If this variable is non-`nil`, Gnus will save the kill file after processing, which is necessary if you use expiring kills.
`gnus-apply-kill-hook`
  A hook called to apply kill files to a group. It is `(gnus-apply-kill-file)` by default. If you want to ignore the kill file if you have a score file for the same group, you can set this hook to `(gnus-apply-kill-file-unless-scored)`. If you don't want kill files to be processed, you should set this variable to `nil`.
`gnus-kill-file-mode-hook`
  A hook called in kill-file mode buffers.

## GroupLens

GroupLens is a collaborative filtering system that helps you work together with other people to find the quality news articles out of the huge volume of news articles generated every day.

To accomplish this the GroupLens system combines your opinions about articles you have already read with the opinions of others who have done likewise and gives you a personalized prediction for each unread news article. Think of GroupLens as a matchmaker. GroupLens watches how you rate articles, and finds other people that rate articles the same way. Once it has found for you some people you agree with it tells you, in the form of a prediction, what they thought of the article. You can use this prediction to help you decide whether or not you want to read the article.

- Using GroupLens: How to make Gnus use GroupLens.
- Rating Articles: Letting GroupLens know how you rate articles.
- Displaying Predictions: Displaying predictions given by GroupLens.
- GroupLens Variables: Customizing GroupLens.

### Using GroupLens

To use GroupLens you must register a pseudonym with your local Better Bit Bureau (BBB). At the moment the only better bit in town is at ``http://www.cs.umn.edu/Research/GroupLens/bbb.html'`.

Once you have registered you'll need to set a couple of variables.

`gnus-use-grouplens`
  Setting this variable to a non-`nil` value will make Gnus hook into all the relevant GroupLens functions.
`grouplens-pseudonym`
  This variable should be set to the pseudonum you got when registering with the Better Bit Bureau.
`grouplens-newsgroups`
  A list of groups that you want to get GroupLens predictions for.

Thats the minimum of what you need to get up and running with GroupLens. Once you've registered, GroupLens will start giving you scores for articles based on the average of what other people think. But, to get the real benefit of GroupLens you need to start rating articles yourself. Then the scores GroupLens gives you will be personalized for you, based on how the people you usually agree with have already rated.

### Rating Articles

In GroupLens, an article is rated on a scale from 1 to 5, inclusive. Where 1 means something like this article is a waste of bandwidth and 5 means that the article was really good. The basic question to ask yourself is, "on a scale from 1 to 5 would I like to see more articles like this one?"

There are four ways to enter a rating for an article in GroupLens.

`r`
  This function will prompt you for a rating on a scale of one to five.
`k`
  This function will prompt you for a rating, and rate all the articles in the thread. This is really useful for some of those long running giant threads in rec.humor.

The next two commands, `n` and `,` take a numerical prefix to be the score of the article you're reading.

`1-5 n`
  Rate the article and go to the next unread article.
`1-5 ,`
  Rate the article and go to the next unread article with the highest score.

If you want to give the current article a score of 4 and then go to the next article, just type `4 n`.

### Displaying Predictions

GroupLens makes a prediction for you about how much you will like a news article. The predictions from GroupLens are on a scale from 1 to 5, where 1 is the worst and 5 is the best. You can use the predictions from GroupLens in one of three ways controlled by the variable `gnus-grouplens-override-scoring`.

There are three ways to display predictions in grouplens. You may choose to have the GroupLens scores contribute to, or override the regular gnus scoring mechanism. override is the default; however, some people prefer to see the Gnus scores plus the grouplens scores. To get the separate scoring behavior you need to set `gnus-grouplens-override-scoring` to `'separate`. To have the GroupLens predictions combined with the grouplens scores set it to `'override` and to combine the scores set `gnus-grouplens-override-scoring` to `'combine`. When you use the combine option you will also want to set the values for `grouplens-prediction-offset` and `grouplens-score-scale-factor`.

In either case, GroupLens gives you a few choices for how you would like to see your predictions displayed. The display of predictions is controlled by the `grouplens-prediction-display` variable.

The following are legal values for that variable.

`prediction-spot`
  The higher the prediction, the further to the right an ``*'` is displayed.
`confidence-interval`
  A numeric confidence interval.
`prediction-bar`
  The higher the prediction, the longer the bar.
`confidence-bar`
  Numerical confidence.
`confidence-spot`
  The spot gets bigger with more confidence.
`prediction-num`
  Plain-old numeric value.
`confidence-plus-minus`
  Prediction +/i confidence.

### GroupLens Variables

`gnus-summary-grouplens-line-format`
  The summary line format used in summary buffers that are GroupLens enhanced. It accepts the same specs as the normal summary line format (see section Summary Buffer Lines). The default is ``%U%R%z%l%I%(%[%4L: %-20,20n%]%) %s\n'`.
`grouplens-bbb-host`
  Host running the bbbd server. The default is ``grouplens.cs.umn.edu'`.
`grouplens-bbb-port`
  Port of the host running the bbbd server. The default is 9000.
`grouplens-score-offset`
  Offset the prediction by this value. In other words, subtract the prediction value by this number to arrive at the effective score. The default is 0.
`grouplens-score-scale-factor`
  This variable allows the user to magnify the effect of GroupLens scores. The scale factor is applied after the offset. The default is 1.

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