Basic Idea:

  slrn awards an article points by giving it a score.  If the score for the
article is less than zero, the article is marked as read or killed.  The
purpose of the score file is to define the set of tests that an article must
go through to determine the score.

Although the score may be based on ANY header item, it is recommended that
one stick with the information found in the news overview data when scoring
in slrn (slrnpull gets full headers anyways, so it does not make a
difference there).  The news overview file typically contains:

      * Subject
      * From
      * Date
      * Message-ID
      * References
      * Bytes
      * Lines

plus any header that your news admin decided to include here (usually,
"Xref" is one of them).  slrn offers two special keywords that also allow
efficient scoring: "Newsgroup" (the newsgroup that the article is part of)
and "Age" (the age of the article in days).

Score file format:

  The format of the file is very simple (See below for an explicit
example). The file is divided into sections delimited by a newsgroup
or newsgroups enclosed in square brackets, e.g.,

     [rec.crafts.*, rec.hobbies.*]

The name may contain the `*' wild card character.  

Comments begin with the `%' character.  Leading whitespace is ignored.

Each section consists of comment lines, empty lines or keyword lines.
Only the keyword lines are meaningful and all leading whitespace is
ignored.  A keyword line begins with the name of the keyword followed
immediately by one or two colons and one space.  The rest of the line
usually consists of a regular expression.  The keyword may be prefixed
by the `~' character to signify that the regular expression should not
match the object specified by the keyword.

A group of keywords defines a test that is given to the header of the
article.  The `Score' keyword is used to assign a score to the header. If it
is followed by a single colon, the score is only given if all tests are
passed (logical AND); two colons indicate that the score should be awarded
if any of the tests are passed (logical OR). The score can be any positive
or negative integer.  If the numerical value of the score is prefixed by an
equal sign, score processing for the header is stopped and the header will
be given the score for that test.

Note: The `Score' keyword also serves to delimit tests. You can optionally
add a comment behind the score, which will then be used as the name of the
scorefile entry and displayed when using view_scores ('v') in article mode.
Here is an example of this:

Score: 100 % optional name here

All keywords except for `Score' and `Expires' may be prefixed by the `~'
character.  If the `Expires' keyword appears, it must immediately follow the
`Score' keyword.  The `Expires' keyword may be used to indicate that the
test is no longer to be applied on the date specified by the keyword.  For
example,

    Expires: 4/1/1996              (or: 1-4-1996)

implies that the given test is no longer valid on or after April first 1996.
As the example indicates, the date must be specified using either the format
MM/DD/YYYY or DD-MM-YYYY.  Note: DO NOT CONFUSE THIS WITH THE EXPIRES HEADER
KEYWORD.

The Lines, Bytes, Age and Has-Body keywords are also special.  Their value
is not a regular expression, rather, a simple integer.

"Lines" and "Bytes" may be used to kill articles which contain too many or
too few lines / bytes.  For example,

    Score: -100
    Bytes: 20480
    
assignes a score of -100 to articles that are larger than 20 kB.  Please
keep in mind that "Bytes:" is only available when getting overview data and
will otherwise (e.g. in slrnpull) be set to 0.

Similarly, the test

    Score: -100
    ~Lines: 3
    
assigns a score to articles that have less than or equal to 3 lines.

"Age" can be used to score articles which are younger than N days. For
example,

    Score: 10
    Age: 7

adds 10 points to the score of each article that is at most one week old.
You can use negation (`~') to score articles that are older than N days.

"Has-Body" can be used when reading offline in combination with slrnpull:
You can tell slrnpull to download only article headers by default and fetch
article bodies on request. In this case, you can use a rule like

    Score: 20
    Has-Body: 1

to give each article that does have a body 20 points. You can invert this
(i.e. score articles without bodies) either by using negation ('~') or by
writing "Has-Body: 0". Other values than 0 or 1 have no meaning.

Finally a score file may include other score files via the `include'
statement.  The syntax is simple:

    include FILE

The name of the file is considered to be relative to the directory of
the file including it.  For instance suppose /home/john/News/Score
contains

    include /usr/local/share/slrn/score
    include score_spam
    
and `/usr/local/share/slrn/score' contains the line:

    include score_spam

In the first instance, score_spam will be read from the directory
/home/john/News but in the second instance it will be read from
/usr/local/share/slrn.

Here is a sample slrn score file:
-------------------------------------------------------------  
  [news.software.readers]
     Score: =1000
     % All slrn articles are good
     Subject: slrn
  
     Score: 1000
     % This is someone I want to hear from
     From: davis@space\.mit\.edu

     Score: -9999
     Subject: \<f?agent\>

  [comp.os.linux.*]
     Score: -10
     Expires: 1/1/1996
     Subject: swap
     
     Score: 20
     Subject: SunOS
      
     Score: 50
     From: Linus
     
     % Kill all articles cross posted to an advocacy group
     Score: -9999
     Xref: advocacy
     ~From: Linus
     
     % This person I want nothing to do with unless he posts about 
     % `gizmos' but only in comp.os.linux.development.*
     
     Score: -9999
     From: someone@who\.knows\.where
     ~Subject: gizmo
     ~Newsgroup: development
  
  [~misc.invest.*, misc.taxes]
     Score:: -9999
      Subject: Earn Money
      Subject: Earn \$
      
--------------------------------------------------------  

This file consists of two sections.  The first section defines a set
of tests applied to the news.software.readers newsgroups.  The second
section applies to the comp.os.linux newsgroups. The final section
applies to ALL newsgroups EXCEPT misc.invest.* and misc.taxes (see
below).

The first section consists of three tests.  The first test applies a score
of 1000 to any subject that contains the string `slrn'.  The second test
applies to the `From'.  It says that any article from davis@space.mit.edu
gets scores 1000.  The third test gives a score of -9999 to any article
whose subject contains the word `agent'.  Since tests are applied in order,
if an article contains both `slrn' and `agent', it will be given a score of
1000 since the value is prefixed with an equal sign.

The second section is more complex.  It applies to the newsgroups
comp.os.linux newsgroups and consists of 5 tests.  The first three are
simple: -10 points are given if the subject contains `swap', 20 if it
contains SunOS, and 50 if the article is from someone named `Linus'.  This
means that if Bill@Somewhere writes an article whose subject is `Swap, Swap,
Swap', the article is give -10 points.  However, if the Linus writes an
article with the same title, it is given -10 + 50 = 40 points.  Note that
the first test expires at the beginning of 1996.

The fourth test kills all articles that were cross posted to an advocay
newsgroup UNLESS they were posted by Linus.  Note that if a keyword begins
with the `~' character, the effect of the regular expression is reversed.

The fifth test serves to filter out posts from someone@who.knows.where
unless he posts about `gizmos' in one of the comp.os.development newsgroups.
Again note the `~' character.

The final section of the score file begins with the line

  [~ misc.invest.*, misc.taxes]

If the first character following the opening square bracket is `~',
then the newsgroup or newsgroups contained in the brackets are NOT to
be matched.  That is, the `~' character is used to denote the boolean
NOT operation.

For writing even more complex entries, slrn now allows the grouping of
scorefile rules. Here is a simple example:

Score:: -1000
	~Subject: \c[a-z]
	{:
	  Subject: ^Re:
	  ~Subject: ^Re:.*\c[a-z]
	}

Lines enclosed in curly braces are grouped; the initial brace is followed by
one or two colons that indicate whether only one (`::') or all of the lines
(`:') inside the group need to match for the group to pass.

As the result, the example kills subject header lines that do not contain
lowercase characters, not counting an initial "Re:".
