Basic Idea:

  slrn awards an article points by giving it a score.  If the score for the
article is less than max_low_score (zero by default), the article is marked as
read.  If the score is less than or equal to kill_score (-9999 by default),
the article is killed.  If the score is greater than or equal to
min_high_score (1 by default), the article is marked as important.  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 equals 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: 4/1/2010              (or: 1-4-2010)

implies that the given test is no longer valid on or after April first 2010.
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, unless an absolute path is specified.  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: \<agent\>

[comp.os.linux.*]
	Score: -10
	Expires: 1/1/2010
	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 three 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 has its
score increased by 1000.  The third test reduces by -9999 the score of 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 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 given
-10 points.  However, if 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 2010.

The fourth test kills all articles that were cross-posted to an advocacy
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:'.
