
  pgn-extract: a Portable Game Notation (PGN) manipulator


    Overview

This file documents a program to extract selected games from a PGN
format data file. There are several ways to specify the criteria on
which to extract: textual move sequences, the position reached after a
sequence of moves, information in the tag fields, and material balance
in the ending. Full ANSI C source for the program is available under the
terms of the GNU General Public License <#license>. The program includes
a semantic analyser which will report errors in game scores and it is
also able to detect duplicate games found in one or more of its input
files.

The range of input move formats accepted is fairly wide and includes
recognition of lower-case piece letters for English and upper-case piece
letters for Dutch and German. The default output is in English Standard
Algebraic Notation (SAN), although there is some support for output in
different notations.

Extracted games may be written out either including or excluding
comments, NAGs, and variations. Games may be given ECO classifications
derived from the accompanying file eco.pgn, or a customised version
provided by the user.


    Index

    * Flag summary <#flag-summary>
    * Usage and Arguments (-f) <#usage>
    * Input Format <#input>
    * Output Files (-o, -a) <#output>
    * Variations: <#variations>
          o Positional Variations (-x) <#-x>
          o Textual Variations (-v) <#-v> 
    * Textual Variation Permutations (-P) <#-P>
    * Duplicate Games (-d and -D, plus -Z) <#duplicates>
    * Suppression of Unique Games (-U) <#-U>
    * Check Files for Duplicates (-c) <#-c>
    * Matching on Tag Criteria (-t) <#-t>
    * Date and Elo Matches with -t <#date-t>
    * Tag Criteria on the Command Line (-T) <#-T>
    * Date Matches with -T <#date-T>
    * Argument Descriptions in a File (-A) <#-A>
    * Outputing Games not matched (-n) <#-n>
    * Setting bounds on the number of moves in a game (-b) <#-b>
    * Matching only games that end in checkmate (-M) <#-M>
    * ECO Classification (-e) <#-e>
    * Separate Output Files (-#, -E) <#separate-output>
    * Soundex Matching (-S) <#-S>
    * Output Line Length (-w) <#-w>
    * Output Format and Language (-W) <#-W>
    * Forsyth-Edwards Notation (FEN) Descriptions (-F) <#-F>
    * Material Matches (-z) <#-z>
    * The Seven Tag Roster (-7) <#-7>
    * User-defined Tag Roster Ordering (-R) <#-R>
    * Mailing List <#mailing>
    * Limitations <#limitations>
    * The Files <#files>
    * Portability <#portability>
    * Acknowledgements <#acknowledgements>
    * License <#license>
    * A History of Changes to the Original Release <#history> 


      Flag summary

There follows a brief summary of the different flags taken by
pgn-extract, such as is produced by the -h flag. You are strongly
advised to read the remainder of this file, however, before attempting
to use extract in earnest.

    * Flags: -7 - output only the seven tag roster for each game. Other
      tags (apart from FEN and possibly ECO/Opening/Variation) are
      discarded (See -e).
    * -aoutputfile - the file to which extracted games are to be
      appended. See -o flag for overwriting an existing file.
    * -Aargsfile - read the program's arguments from argsfile.
    * -b[elu]num - restricted bounds on the number of moves in a game.
          o lnum set a lower bound of 'num' moves,
          o unum set an upper bound of 'num' moves,
          o otherwise num (or enum) means equal-to 'num' moves. 
    * -cfile[.pgn] - Use file as a list of check files for duplicates.
    * -C - don't include comments in the output. Ordinarily these are
      retained.
    * -dduplicatefile - the file to which duplicate extracted games are
      to be written.
    * -D - don't output duplicate extracted game scores.
    * -eECO_file - perform ECO classification of games. The optional
      ECO_file should contain a PGN format list of ECO lines Default is
      to use eco.pgn from the current directory.
    * -E[123 etc.] - split output into separate files according to ECO.
          o E1 : Produce files from ECO letter, A.pgn, B.pgn, ...
          o E2 : Produce files from ECO letter and first digit, A0.pgn, ...
          o E3 : Produce files from full ECO code, A00.pgn, A01.pgn, ...
          o Further digits may be used to produce non-standard further
            refined division of games. 
      All files are opened in append mode.
    * -ffile_list - file_list contains the list of PGN files to be
      searched - one per line.
    * -F - output a FEN string comment of the final game position.
    * -h - print an abbreviated list of help.
    * -h1 - print further help.
    * -? - print an abbreviated list of help.
    * -llogfile - Create a new logfile for the diagnostics rather than
      using stderr.
    * -Llogfile - Append all diagnostics to logfile.
    * -M - Match only games which end in checkmate.
    * -noutputfile - Write all valid games not otherwise output to
      outputfile.
    * -N - don't include NAGs in the output. Ordinarily these are retained.
    * -ooutputfile - the file to which extracted games are to be
      written. Any existing contents of the file are lost (see -a flag).
    * -P - don't match permutations of the textual variations (-v).
    * -r - report any errors but don't extract.
    * -Rtagorder - Use the tag ordering specified in the file tagorder.
    * -s - silent mode don't report each game as it is extracted.
    * -S - Use a simple soundex algorithm for tag matches. If used, this
      option must precede the -t or -T options.
    * -ttagfile - file of player, date, or result, extraction criteria.
    * -Tcriterion - player, date, or result, extraction criteria.
    * -U - don't output games that only occur once. (Use with -d to
      identify duplicates in multiple files.)
    * -vvariations - the file variations contains the textual lines of
      interest.
    * -V - don't include variations in the output. Ordinarily these are
      retained.
    * -wwidth - set width as an approximate line width for output.
    * -W - don't rewrite the moves into Standard Algebraic Notation.
    * -W[cm|epd|halg|lalg|elalg|san] - specify the output format to use.
          o Default (i.e., without this flag) is SAN.
          o -W (without anything following) selects the input format.
          o -Wcm is a legacy option that wrote ChessMaster format. I
            don't know if the output produced is still valid.
          o -Wepd is EPD format.
          o -Whalg is hyphenated long algebraic.
          o -Wlalg is long algebraic
          o -Welalg[PNBRQK] is enhanced long algebraic. Use the
            characters PNBRQK for language specific output, e.g:
            -WelalgBSLTDK for German.
          o -Wsan[PNBRQK] Use the characters PNBRQK for language
            specific output, e.g: -WsanBSLTDK for German. 
    * -xvariations - the file variations contains the lines resulting in
      positions of interest.
    * -zendings - the file endings contains the end positions of interest.
    * -Z - use the file virtual.tmp as an external hash table for
      duplicates. Use when MallocOrDie messages occur with big datasets.
    * -#num - output num games per file, to files named 1.pgn, 2.pgn, etc. 

Error messages and verbose reporting is done to the standard error
output unless the -l/-L flag is used.


    Usage and Arguments (-f)

Extract takes an arbitrary number of game scores as input and outputs
zero or more of these games, typically in English Standard Algebraic
Notation (SAN). Which of the input games are output, and the style of
the output, depend upon the particular set of command line flags passed
to pgn-extract. The general form for calling pgn-extract is as follows:

    pgn-extract [flags] [input-game-files]

In its simplest form, calling pgn-extract with no arguments will cause
it to read games from its standard input, check them and reproduce those
without errors in SAN notation on its standard output.

Normally, the input files from which games are to be extracted are
listed on the command line:

    pgn-extract file1.pgn [file2.pgn ...]

An alternative to listing the game files on the command line is to list
their names, one per line, in a file which is then given after the -f flag:

    pgn-extract -ffile_list

In order to save the output in a file rather than standard output, use
either -o or -a <#output> to indicate the output file name, for instance:

    pgn-extract -oall.pgn file1.pgn file2.pgn file3.pgn

While pgn-extract can be used simply to check and reformat all the input
games, it is more usual to use it to select subsets of the input games.
Several different criteria are available on which to extract: move
variations <#variations>, information in the tag fields <#-t>, and
material balance in the ending <#-z>, for instance. All of these
criteria are described in detail below.


    Input Format

This program's principle aim is to be able to read PGN files and output
games of interest. It follows that the input should look reasonably like
PGN to start with. This means that it doesn't cope well with files that
contain news article or mail headers, for instance, although it does
make an attempt to skip text that is obviously not game related between
games. Having said that, it does not require the move text be in
Standard Algebraic Notation (SAN). It will accept quite a few common
formats including:

    * Algebraic
    * Long Algebraic
    * various commonly-used intervening characters, such as : - x
    * Dutch and German upper case piece letters. (Support for Russian
      piece letters is in prototype.)
    * lower-case English piece characters (except that it will always
      prefer 'b' to mean a pawn move rather than a Bishop move). 

It does not require that there be any move numbers or PGN headers
preceding a game, as long as the move text is terminated by a valid
result designation: *, 1-0, 0-1, 1/2-1/2 (1/2 is also accepted). This
makes the program reasonably suitable for entering raw game text and
having it reformatted in proper SAN with a full set of headers.


    Output Files (-o, -a)

In order to output all matched games to a single new file, the -o flag
is used:

    pgn-extract -onew.pgn file1.pgn file2.pgn

This has the effect of creating new.pgn from the contents of file1.pgn
and file2.pgn. The games in both source files are checked and rewritten,
if necessary, into SAN. Any previous contents of new.pgn will be lost
with the -o flag. In order to avoid this and append to an existing file,
use the -a flag:

    pgn-extract -anew.pgn file1.pgn file2.pgn

Note that there should be no space between either -o or -a and the
output file name.


    Variations (-v and -x)

There are two distinct ways to specify variations of interest;
positional variations (the -x flag <#-x>) and textual variations (the -v
flag <#-v>). The major difference between the two is that positional
variations specify a complete move sequence whose end position is the
primary point of interest, whereas textual variations allow incomplete
and fuzzy move sequence matches on the text of a game to select games.
Whilst it is possible to use both flags together, this would be unusual
as a game must match with both to be extracted.


    Positional Variations (-x)

The variations in which you are interested should be placed in a file
whose name is supplied with the -x flag. For instance:

    pgn-extract -xvars

where each variation is listed on a single line in the file vars (the
filename is immaterial). The following set of moves:

    e4 c5 Nf3 d6 d4 cxd4 Nxd4 Nf6 Nc3 a6

indicates that you wish to pick up all games reaching the Najdorf
variation position of the Sicilian Defence. Games reaching the end
position of this sequence are selected regardless of the route that was
taken to reach it. This allows various transpositional sequences to be
specified by quoting just one line to reach the required point.
Therefore, games employing the following move order will be picked up by
quoting the line above.

    e4 c5 Nc3 d6 Nge2 Nf6 d4 cxd4 Nxd4 a6

A position is considered to match a required variation if it generates
the same board hash value. In the interests of reasonable efficiency, no
attempt is made to actually examine the state of the board. There is,
therefore, the potential for false hits but in my usage of pgn-extract I
have not found this to be a problem.

With this option, games are only searched to a depth approximately equal
to the length of the longest positional variation, in order to make
processing of large data sets faster than with a search of the whole game.

A comment line may be placed in a variation file by using a '%' as the
first character of the line. Move numbers are optional within the list
of moves.

From version 14.0 onwards, an alternative form of positional match is
available using a FEN description of the desired position. See the
description of the -t flag <#-t> for how to specify a FEN position, and
the -F flag <#-F> for a simple way to generate a FEN description from a
game score.


    Textual Variations (-v)

With this option, the matching is purely textual in nature, in contrast
to the -x flag <#-x>. The -v flag works by string matching on the input
text of moves, so there is no facility for picking up transpositions
automatically. The variations in which you are interested should be
placed in a file whose name is supplied with the -v flag. For instance:

    pgn-extract -vvars

Each variation should be listed on a single line in the file vars (the
filename is immaterial). The move sequence:

    e4 c5 Nf3 d6 d4 cxd4 Nxd4 Nf6 Nc3 a6

indicates that you wish to pick up all games following the normal move
order of the Najdorf variation of the Sicilian Defence, and

    d4 Nf6 c4 e6 Nc3 Bb4

that you are interested in Nimzo-Indian games. The order in which the
moves are played by either White or Black is immaterial. All
combinations are tried, so the ordering:

    c4 e6 Nc3 Bb4 d4 Nf6

will produce the same set of matches as the previous ordering of the
Nimzo-Indian moves (see the -P flag <#-P> for how to prevent this).

A comment line may be placed in a variation file by using a '%' as the
first character of the line. Move numbers are optional within the list
of moves.

As transpositions are not picked up automatically with this flag, if you
also wanted to recognise the following as a Najdorf, you would have to
add this line to the variations file in addition to that given above:

    e4 c5 Nc3 d6 Nge2 Nf6 d4 cxd4 Nxd4 a6

However, because of the way in which the matching is done, it is
possible to specify slight alternatives on the way in which individual
moves are written. Notational alternatives for a single move are just
written separated from each other with a non-move character. This
variation specifies both the shorter and longer ways of writing the
captures in a Najdorf:

    e4 c5 Nf3 d6 d4 cxd4|cd Nxd4|Nd4 Nf6 Nc3 a6

However, given the variety of possible ways of writing various moves in
non-SAN format, e.g.

    cxd4|cd|c5d4|c5-d4

variation lists can get quite messy and I believe that this approach is
best avoided by ensuring that the input is proper SAN and only using SAN
notation in the variations file. In this way, the alternative-separator
can then be used purely for indicating genuine alternative moves at that
point, e.g.

    e4 c5 Nf3 d6 d4|d3

An important point when listing moves is that check and mate indicators
should be included where appropriate, otherwise moves incorporating
these characters in games to be searched will fail to match.

There is little point in using the -v flag in preference to the -x flag
<#-x> if you are only interested in finding games that reach a
particular position. The real use for -v is when you wish to pick up
games in a more general way. For instance, the character '*' may be used
in place of any move to indicate that you don't care what was played at
that point. So the following:

    * b6

means that you are interested in all games in which Black replied 1 ...
b6 regardless of White's first move. The sequence:

    d4 * c4 * Nc3 *

will pick up Nimzo-Indian, Grunfeld, King's Indian, etc. defences. This
notation is not possible with positional variations <#-x>.

In addition, the character '!' may be used in front of any move to
indicate that you wish to disallow particular moves from matching at
this point. For instance, if you want to find Sicilian games where White
did not reply with Nf3 at move 2 you would specify:

    e4 c5 !Nf3

If you wished to disallow 2.Ne2 as well then

    e4 c5 !Nf3|Ne2

does the job. (Adding parentheses makes no difference as the '!' is
applied to all of the following move string.)

Care should be taken combining '!', '*' and variation permutations (see
the -P flag <#-P>). Disallowed moves take precedence over '*' moves. If
a single disallowed move is found in a game within the length of the
variation, that game is excluded. This was the most sensible
interpretation that I could find to place on this usage.


    Textual Variation Permutations (-P)

Normally, all permutations of a textual variation (see the -t flag
<#-t>) are tried against the moves of a game. This cuts down on the
number of separate transpositional orderings that it is necessary to
list, at the cost of slower matching of each game. If the following were
used to look for Nimzo-Indian games:

    d4 Nf6 c4 e6 Nf6 Nc3 Bb4

a side-effect would be that it will also pick up games which start as:

    1. c4 Nf6 2. Nc3 e6 3. d4 Bb4

for instance. The -P flag requests that textual variations are matched
against the moves of the game strictly in the order in which they are
listed, without trying different orders. So, if you want to find only
those games that follow a particular move order, use this flag to
suppress permutations.


    Duplicate Games (-d and -D, plus -Z)

If either the -d or -D flag is used, pgn-extract attempts to recognise
duplicate extracted games. Using the -d flag indicates that you wish
copies of the duplicate games to be written to the indicated file:

    pgn-extract -ddupes.pgn -ounique.pgn file.pgn

will extract from file.pgn the unique set of games into unique.pgn and
the duplicates (i.e., the second and subsequent copies of a game) to
dupes.pgn. A comment identifying in which file a duplicate was found
precedes the first duplicate found in that file and each duplicate game
has a prefix comment indicating the file in which the first version was
found.

With the -D flag duplicate games are suppressed from the output. These
two flags are mutually exclusive, therefore.

Duplicates are identified by comparing a hash value for the board of the
end positions of extracted games and an additional cumulative hash value
generated from the move sequence. If these both values match then games
are considered to be duplicates. This is not guaranteed to be exact but
it gives a good approximation.

You should note that games are only considered to be duplicates on the
basis of the moves played. It may be that a game considered to be a
duplicate contains annotations and variations not present in the one
found earlier, so it might be necessary to do some swapping around to
obtain those you really wish to retain. You should, therefore, use the
-D flag with caution if you are trying to reorganise your master
collection rather than selecting out specific games for examination.
(See also the -U flag <#-U>.)

Detecting duplicates requires memory for the storage of a hash table
containing information on each game. No attempt is made to use extended
or expanded memory and so large databases can result in a MallocOrDie
error. If this is the case, try using the -Z flag which forces
pgn-extract to store its hash table externally, in a file called
virtual.tmp. Each game requires 16 bytes of file space. Clearly, if a
very large database is being processed, there is a risk of filling up
the available file space if there is insufficient available.


    Suppression of Unique Games (-U)

The -U flag suppresses output of the first occurrence of a particular
game. This is useful when combined with the -d flag <#duplicates> as a
means of identifying just those games that are duplicated in a list of
multiple files. As the duplicate games are commented with the file in
which they were located, it then becomes possible to prune a set of
files containing common games. For instance, suppose oldfile.pgn
contains a set of games without duplicates, and you wish to know which
games in newfile.pgn already occur in oldfile.pgn:

    pgn-extract -U -ddupes.pgn oldfile.pgn newfile.pgn

will write to dupes.pgn the duplicate games so that you can go through
newfile.pgn and remove them. Of course, if you simply want to hold the
combined set of games in a single file you would use something like:

    pgn-extract -D -onewset.pgn oldfile.pgn newfile.pgn

See Duplicate Games <#duplicates> for dealing with MallocOrDie errors.


    Check Files for Duplicates (-c)

Check files contain games that are to be used in duplicate detection,
but not to form part of the output. If the filename appended to the
argument has a .pgn/.PGN suffix it is assumed to be a single file of
games. If it does not have this suffix then it is assumed to be a file
containing a list of the names of PGN game files, one per line, to be
used as check files. A typical use for this is to select new games of
interest from a file that probably contains games that exist elsewhere.
In the following example, we wish to select Nimzo-Indian games from
newfile.pgn that don't already occur in the master file nimzo.pgn:

    pgn-extract -cnimzo.pgn -vnimzo.var -D -onewnimzo.pgn newfile.pgn

The games in nimzo.pgn act as the source for duplicate detection so
duplicates of these will be suppressed (the -D flag <#duplicates>). Only
those games from newfile.pgn which are not in nimzo.pgn will be output
to newnimzo.pgn. Contrast this behaviour with the following, which would
create a new master file of games from the combination of nimzo.pgn and
newfile.pgn:

    pgn-extract -vnimzo.var -D -onewnimzo.pgn nimzo.pgn newfile.pgn


    Matching on Tag Criteria (-t)

There are two ways to specify that you wish to use information in the
tag fields as extraction criteria: the -t flag and the -T flag <#-T>.
The -t flag takes a file name argument and is the preferred method
because of its ease of use and greater flexibility:

    pgn-extract -ttags games.pgn

where tags is an arbitrary file name. In the file are listed tag name
and value pairs corresponding to the extraction criteria you wish to
use. Each line of this file should be of the form:

    PGN-Tag-name Tag-string

for instance:

    White "Tal"

(note the need to include double quotes around the tag value). This
requests that only those games where Tal had the White pieces are to be
considered for extraction. If you wish to limit the year in which those
games were played you might list:

    White "Tal"
    Date "1962"

Multiple pairs with the same tag name are or-ed together so:

    % Find games in the period 1960-1962.
    Date "1960"
    Date "1961"
    Date "1962"

will select all games from the three listed years. Note that comments
may be included in the tag file.

In general, tags names that differ are and-ed together, so:

    White "Tal"
    Black "Fischer"
    Date "1962"
    Result "1-0"

selects only those games that Tal won with the White pieces against
Fischer in 1962.

It is important to note that:

    White "Tal"
    Black "Tal"

does not find all games played by Tal, but only those that he played
against himself. In order to overcome this, I have introduced a non-PGN
tag that should only be used in the extraction criteria file:

    Player "Tal"
    Date "1962"

finds all games from 1962 in which Tal had either the White pieces or
the Black. In effect, the White and Black player lists are or-ed
together rather than and-ed using this pseudo-tag.

Prefix matching on tag values is done so that a criterion should be a
prefix of the complete Tag string. Thus,

    Player "Karpov"

would match:

    [White "Karpov"]
    [White "Karpov, A"]
    [White "Karpov, An"]
    [White "Karpov, Alexander"]

but not

    [White "Anatoli Karpov"]

See the -S <#-S> flag for a soundex facility with tag matching.

All tag criteria except ECO classification are checked before the moves
of the game in the interests of efficiency (tag checking is relatively
fast whereas positional checking of the game is not). Only once the game
has been processed is it checked to see whether an ECO tag match has
been requested. The consequence of this is that using the -e flag <#-e>
in combination with ECO tag criteria you can search for games in
particular ECO lines without an ECO tag having been present in the input
form.

From version 14.0 onwards, use of a FEN tag with the -t flag has a
special meaning. Rather than using this to match FEN tags in the header
of a game, a FEN description is used to indicate a search for a
positional match (similar to use of the -x <#-x> flag). If a FEN
description is provided with the -t flag, the indicated position is
searched for in each game processed, and only those games that reach the
indicated position are output. A FEN tag-pair for the starting position
would be described by:

    FEN "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"

The position after the two moves e4 c5 would be:

    FEN "rnbqkbnr/pp1ppppp/8/2p5/4P3/8/PPPP1PPP/RNBQKBNR w KQkq c6 0 2"

See details of the -F flag <#-F> for a simple way to generate a FEN
description from a game score.


      Date and Elo Matches with -t

From a -t tag file <#-t>, more complex matching of dates and Elo values
may be performed by placing an operator between the tag name and the tag
string to be matched:

    Date < "1962"

would only match games played before 1962. Only the year value
participates in the matching process, as this is done using integer
values rather than strings.

    WhiteElo >= "2500"

only matches games where White is a strong player. Probably of more
general use is another pseudo-tag that I have introduced purely for this
purpose: Elo.

    Elo >= "2500"

matches games in which either player has an Elo tag matching that
relationship. The operators allowed are >, >=, <, <=, =, and <> (not
equal to).


    Tag Criteria on the Command Line (-T)

An alternative to the -t flag <#-t> is the -T flag, for use where
command line arguments are more convenient - perhaps where pgn-extract
is being invoked from another program. The tag coverage is not as
extensive as with a tag file, and the syntax is rather cumbersome. It is
used as follows: after the -T comes a single letter from the limited set
[bdprw] to select string prefixes of the tag fields of a game. For
instance:

    * -TwPlayer - Extract games where Player has the White pieces.
    * -TbPlayer - Extract games where Player has the Black pieces.
    * -TpPlayer - Extract games where Player has either colour.
    * -TdDate - Extract games played on Date.
    * -TrResult - Extract games with result Result.
    * -TaAnnotator - Extract games Annotated by Annotator.
    * -TeEco - Extract games with ECO designation Eco. 

For example,

    pgn-extract -TwTal -TbFischer file.pgn

would extract games from file.pgn in which Tal had the White pieces and
Fischer the Black.

Criteria of the same tag type are or-ed together, so

    pgn-extract -Tr1-0 -Tr0-1 file.pgn

extracts only decisive games.

Criteria of different tag types are and-ed together so

    pgn-extract -TwTal -Td1962 -Tr1-0 file.pgn

would extract only those games in which Tal played with the White pieces
in 1962 and won.

The ECO classification (see the -e flag <#-e>) is performed before
attempting to match an ECO tag, so:

    pgn-extract -TeA01 -e file.pgn

will perform ECO classification on the input file and extract games with
ECO classification A01 (Nimzo-Larsen attack), for instance.


    Argument Descriptions in a File (-A)

It can be inconvenient to repeatedly type long argument lists on the
command line. The -A flag makes it possible to list arguments in a file,
rather than on a command line. Each argument line within the file must
be immediately preceded by a ':' (colon) character. Consider selecting
games by Tal from a file caro.pgn and writing them to talgames.pgn.
Using command line arguments, this would have the following form:

    pgn-extract -TpTal -otalgames.pgn caro.pgn

We can do the same job placing the argument list in the file args:

    % Select games by Tal.
    :-TpTal
    % Where to output the matched games.
    :-otalgames.pgn

and the same selection made with:

    pgn-extract -Aargs caro.pgn

Note that comments may be included using a '%' character.

Each argument should be listed on its own line, and all the arguments
are available in this way. The PGN source files may also be listed in
the argument file. They must be listed one per line, with a preceding
colon character. So an alternative for the above would be:

    % Select games by Tal.
    :-TpTal
    % Where to output the matched games.
    :-otalgames.pgn
    % The game files to be read.
    :caro.pgn

and the command invoked as simply:

    pgn-extract -Aargs

The -t <#-t>, -v <#-v>, -x <#-x>, -z <#-z>, and -R <#-R> flags have
slightly special treatment in an argument file. Where the tags,
variations, positions, endings and/or roster ordering are to be read
from files of those names, say, then the format of these arguments in
the argument file might be as you would expect:

    :-ttags
    :-vvariations
    :-xpositions
    :-zendings
    :-Rroster

However, within an argument file, the file names are optional, and it is
also possible to list further data for these flags on lines immediately
following. For instance, an alternative to:

    :-TpTal

we could say:

    :-t
    Player "Tal"

Notice that no colon should be present on the lines following the flag
line. In the following example, we select games won by Tal as White
reaching a particular position in the Caro Kann:

    :-t
    White "Tal"
    Result "1-0"
    :-otalwins.pgn
    :-x
    e4 c6 d4 d5 exd5 cxd5
    % Which game files to process.
    :caro.pgn

The arguments file may, itself, also contain -A arguments. This should
make it possible to build up hierarchies of game selection criteria if
desired. However, beware that there is no check for circularities in the
dependencies.


    Outputting Games not Matched (-n)

The -n flag will cause all valid games not output via other criteria to
be saved in a given file. The purpose of this is to make it easier to
reorganise files in different ways. For instance, if you wish to remove
all of the games played by Tal from one file, you might do:

    pgn-extract -TpTal -otalgames.pgn -nothers.pgn file.pgn

After which, the file others.pgn will contain all of the valid games
from the original file, with the exception of Tal's.


      Date Matches with -T

A simple form of relational date matching is available from the command
line (-T <#-T>). A date year may be prefixed with either 'b' or 'a' in
order to match games played either before or after the specified date.
This assumes that the date is stored in the game's date tag string in
the normal form: YYYY.MM.DD

So,

    pgn-extract -Tdb1962 file.pgn

will look for games played before 1962. A much fuller capability is
available in tag files with the -t flag <#-t>.


    Setting bounds on the number of moves in a game (-b)

The -b flag allows you to select games which have a number of moves
within the bounds you set. You can set a lower bound on the number of
moves by using -bl ('l' = lower bound), or an upper limit by using -bu
('u' = upper bound). Both are followed by the number of moves so

    pgn-extract -bu20 file.pgn

will find brevities of 20 moves or less, whilst

    pgn-extract -bl60 file.pgn

will find games of 60 moves or move. Bounds may be combined so

    pgn-extract -bl30 -bu40 file.pgn

will find games in the range [30..40] moves. If neither 'l' nor 'u' is
used, but just a number following the -b, this means that the number of
moves must exactly match that number. Alternatively, 'e' can be used to
stand for 'equal to'. The following are equivalent and find all games of
exactly 35 moves.

    pgn-extract -b35 file.pgn
    pgn-extract -be35 file.pgn


    Matching only games that end in checkmate (-M)

The -M flag requests that only games that end in checkmate are matched:

    pgn-extract -M file.pgn


    ECO Classification (-e)

A PGN file of ECO classifications
<ftp://ftp.cs.kent.ac.uk/pub/djb/Extract/eco.pgn> is distributed with
this version. I believe that this was put together by Ewart Shaw, Franz
Hemmer and others, to whom appropriate thanks is due. The -e flag
requests pgn-extract to add/replace ECO classifications in the games it
outputs. This is done by firstly reading a file of ECO lines in PGN
format (eco.pgn in the current directory, by default) and building a
table of resulting positions. As the games are then read they are looked
up in the table to find a classification. The deepest match is found. A
match is allowed within six half moves of the length of the ECO line.
The supplied file has ECO, Opening, and Variation tag strings for many
lines. If present, pgn-extract will add/replace these as well as
SubVariation tags if available.

An alternative file to the default eco.pgn may be supplied in two ways:
either appending a file name to the -e

    -emy_eco_codes

or by setting the environment variable ECO_FILE to the full path name of
the file. Under DOS this can be done with

    set ECO_FILE=eco-file-path

in the AUTOEXEC.BAT file. Under UNIX csh this can be done with

    setenv ECO_FILE eco-file-path

in the .cshrc, for instance.

Having the ECO data read as plain text on program startup has the
obvious disadvantage that there is a high initial time overhead. On the
other hand, it has the advantage that users may add their own
classifications to the file very easily. It is fairly demanding of
memory, so you advised not to combine this with duplicate detection (-U
<#-U>, -D and -d <#duplicates>), which can also consume a lot of memory
with big databases.

Because an ECO tag match with either the -t flag <#-t> or the -T flag
<#-T> is delayed until after ECO classification, this makes it
relatively easy to select games with particular ECO codes even if they
weren't present in the source form.

Usage of -e with the Seven Tag Roster flag (-7 <#-7>) results in the ECO
tags (ECO, Opening, Variation, SubVariation) being included in the
output games.


    Separate Output Files (-#, -E)

The -# and -E flags permit the output to be split into multiple files.
However, be warned that where the input involves a lot of games, these
flags might result in the creation of a large number of output files.

The -# flag takes an unsigned integer argument specifying the maximum
number of games to output to a single file. Successive output files are
numbered 1.pgn, 2.pgn, etc. Any existing contents of these files are
always overwritten on each run of pgn-extract.

       pgn-extract -#250 file.pgn

will check and split file.pgn into separate files of, at most, 250 games
each.

       pgn-extract -#1 file.pgn

will split file.pgn into separate files containing only a single game each.

The -E flag normally takes a numeric argument of value 1, 2, or 3. This
is used to indicate the level of subdivision required based upon the ECO
tag found in a game.

       pgn-extract -E3 file.pgn

will fully subdivide file.pgn into separate files based on the full ECO
code of each game, with names such as B03.pgn, A01.pgn, D45.pgn, etc. If
a game does not contain an ECO tag, or the tag appears to be malformed,
it will be written to a file called, noeco.pgn. All of these files are
written to in append mode, so that existing contents are not lost.
However, beware of using an input file whose name is the same as one
that will be written to by this operation. This could lead to infinite
operation.

Level 1 classification uses just the initial letter of the ECO
classification to append to files A.pgn, B.pgn, etc. Level 2 uses the
initial letter and first digit, producing A0.pgn, B3.pgn, etc.

In fact, values greater than 3 may be used to produce separation of even
finer granularity if more than two digits have been used in the
classification of a game.


    Soundex Matching (-S)

There is a simple soundex algorithm available that attempts soundex
matches on White, Black, Site, Event, and Annotator tags if the -S flag
is used in combination with either the -t flag <#-t> or the -T flag
<#-T>. The -S flag should precede all -t and -T arguments. It should be
noted that the soundex matching does produce false matches.


    Output Line Length (-w)

The -w flag allows an approximate line width to be set for output. The
default value is 75 characters. The following request output lines to be
approximately 100 characters wide:

    pgn-extract -w100 file.pgn


    Output Format and Language (-W)

By default, pgn-extract rewrites the game score into English Standard
Algebraic Notation (SAN) because it is reasonably flexible about the
input form that it will accept. To prevent it from rewriting the
original form of the moves it reads, use the -W flag.

    * By itself, -W outputs the moves using the input text.
    * -Whalg writes them in hyphenated long algebraic (e.g., e2-e4).
    * Using -Wlalg writes the moves in long algebraic form (e.g., e2e4).
    * Using -Welalg writes the moves in enhanced long algebraic form
      (e.g., Ne2e4, e5d6ep). The purpose of enhanced long algebraic form
      is to reduce the amount of chess-specific knowledge that a
      post-procesing program might need in order to interpret a chess
      program. For instance, in order to provide a visualisation. 

Output using non-English piece letters is possible using a variation of
the -Wsan flag. This flag may have a six-letter suffix indicating the
letters to be used in representing pawn, knight, bishop, rook, queen and
king in game scores and diagrams. So:

    pgn-extract -WsanPNBRQK ...

would output in the (default) English notation, and

    pgn-extract -WsanBSLTDK ...

would output in German. Note that the letter for a pawn is required
because board positions are sometimes output when an error is detected
in a game score.

-Wepd was introduced in version 15.0 to output in EPD (Extended Position
Description). A game is output as a sequence of EPD descriptions of the
position at the start of the game, and following each move. Each EPD
line contains the FEN board description, the active colour, castling
availability and en passant target square. A c0 comment contains a
synopsis of the player, event, site and date tags from the game's header.

-Wcm is a legacy flag and outputs the moves in what I believe to be (or
used to be) ChessMaster format.


    Forsyth-Edwards Notation (FEN) Descriptions (-F)

The -t flag <#-t> makes it possible to use Forsyth-Edwards Notation
(FEN) in the description of a position to be matched. The -F flag
provides a convenience method for generating a suitable FEN description
of an arbitrary position. The -F flag causes pgn-extract to output a FEN
description of the final position reached in a game, within the text of
a comment. For instance, suppose you were interested in finding games
that reach the position after the following moves.

    d4 Nf6 c4 e6 Nf3 b6 Nc3 Bb7 e3 Bb4 Bd3 O-O O-O Bxc3 bxc3 c5 *

Storing these moves in the file fen.pgn and running

    pgn-extract -F fen.pgn

would generate the score:

    [Event "?"]
    [Site "?"]
    [Date "????.??.??"]
    [Round "?"]
    [White "?"]
    [Black "?"]
    [Result "*"]

    1. d4 Nf6 2. c4 e6 3. Nf3 b6 4. Nc3 Bb7 5. e3 Bb4 6. Bd3 O-O 7. O-O Bxc3 8.
    bxc3 c5 
    { "rn1q1rk1/pb1p1ppp/1p2pn2/2p5/2PP4/2PBPN2/P4PPP/R1BQ1RK1/ w - c6 0 9" } *

This FEN string could then be cut and pasted to an argument file <#-A>
and used with the -t flag <#-t> to supply matches:

    :-t
    FEN "rn1q1rk1/pb1p1ppp/1p2pn2/2p5/2PP4/2PBPN2/P4PPP/R1BQ1RK1/ w - c6 0 9"

(Note that the FEN string output with -F does not attempt to record the
number of halfmoves since the last pawn move or capture.)


    Material Matches (-z)

The -z flag takes a filename of material balances for which you wish to
search in games. The basic structure of the file is one or more lines of
the form

    pieces1 pieces2

Pieces1 and pieces2 are lists of English piece letters for the material
for the two sides that you wish to look for in a game. For instance:

    rp nb

looks for an game in which a lone Rook and Pawn for one side are
competing against a lone Knight and Bishop for the other. The case of
the letters is immaterial, there is no need to include Kings in the
description, and the order of the pieces does not matter. Apart from
Kings, if a piece letter is not listed for a side then then that piece
is not present within that side's material. A match will be tested for
from both White and Black's point of view, so the example above matches
the same games as:

    nb rp

Some notation may be added after any piece letter, typically to indicate
something about the number of occurrences of that piece on one side.

The following are valid for each piece:

    * * (zero or more of that piece).
    * + (one or more of that piece).
    * d (exactly d occurrences of that piece, where d is a digit).
    * d+ (d or more occurrences of that piece).
    * d- (d or fewer occurrences of that piece). 

So:

    QR2B2N2P8 QR2B2N2P8

is the starting material position, and QR+B*N*P7- represents material in
which we require at least one pawn to be missing from one side and they
should have a Queen and Rook, but we don't care about the minor pieces.

In addition, some extra notation is available to specify material
relative to the opponent's. These are placed after the piece letter to
which they refer.

    * = (the number of these pieces must be the same as the opponent's).
    * # (the number of these pieces must be different the opponent's).
    * > (the number of these pieces more than the opponent has).
    * < (the number of these pieces less than the opponent has). 

So,

    R+P+ R=P#

looks for Rook and Pawn games that with an equal number of Rooks but
unbalanced pawns.

In addition > and < may be preceded by a digit:

    * d> (the number of these pieces must be at least d more than the
      opponent's).
    * d< (the number of these pieces must be at least d less than the
      opponent's). 

Two more notations, >=, <= may be preceded by an optional digit (the
default is 1). The meaning of this may not be intuitively obvious and,
to an extent, they represent a notational compromise.

    * d>= (the number of these pieces must be exactly d more than the
      opponent's).
    * d<= (the number of these pieces must be exactly d less than the
      opponent's). 

In this example, both sides have a pair or Rooks but one has exactly one
pawn more than the other:

    r2p* r=p1>=

Here is an example where one side has sacrificed a Rook and Pawn for
Knight and Bishop and we don't care whether Queens are on or off the
board, so long as they are balanced:

    q*r+n*b*p+ q=r<n>b>p1<

This example represents some of the imprecision that can occur with
matches. The meaning of 'r<' is such that this could match positions in
which one side as 2 Rooks and the other none. This can be corrected with:

    q*r+n*b*p+ q=r1<=n>b>p1<

enforcing strictly one Rook less. We ought also to correct the same
problem with the minor pieces:

    q*r+n*b*p+ q=r1<=n1>=b1>=p1<

In practice, we probably want to allow general matching of minor pieces
so the letter 'L' may be used to stand for a minor piece (Bishop or
Knight). This example represents a similar sacrifice of Rook and Pawn
for two minor pieces.

    q*r+l*p+ q=r1<=l2>=p1<

I would advise against mixing the minor piece letter with Knight and
Bishop letters in the piece set for a single side, however, as I am not
convinced that it will produce exact results.


      Position Stability with -z

The piece sets may be preceded by an optional number indicating the
required stability of the position. Normally, if you are looking for a
position with a particular set of material characteristics then you
probably want that position to last for a reasonable number of moves in
order to study its characteristics. The number before the piece sets is
how many half-moves you wish that material balance to last. By default,
this has a value of 2 so that fleeting positions in the middle of pairs
of exchanges do not produce unwanted matches. This example looks for
double-Rook and pawn games that last at least 10 half-moves:

    10 R2P+ R=P*

Text may be added after the piece lists as a form of comment.

A comment line may be placed in a material balance file by using a '%'
as the first character of the line.


    The Seven Tag Roster (-7)

This flag discards tag pairs that are not part of the Seven Tag Roster:

    Event, Site, Date, Round, White, Black and Result.

However, if the original game included a FEN tag, this is included in
the output, as the moves will make no sense otherwise. In addition, if
the -e flag <#-e> has been used for ECO classification, any ECO,
Opening, Variation and SubVariation tags are also output.


    User-defined Tag Roster Ordering (-R)

The -R flag makes it possible for to define the order in which tags for
a game are listed in the output. The flag should be immediately followed
by the name of a file that contains a list of tag names, one per line,
for instance:

    pgn-extract -Rroster file.pgn

where roster might contain:

    % Output the tags of the seven tag roster alphabetically.
    Black
    Date
    Event
    Result
    Round
    Site
    White

The '%' character may be used to include comments in the file. Tags not
listed in such a file will appear after the required tags have been output.


    Mailing List

If you find the program useful and would like to be put on a mailing
list to receive news of updates or to share suggestions that you think
others might be interested in, then drop me a line at
D.J.Barnes@kent.ac.uk <mailto:d.j.barnes@kent.ac.uk>


    Limitations

The moves, variations, and commentary of each game are held internally
and reformatted when a game is extracted, rather than reproducing the
original text of the game source.

Lower-case 'b' as the first character of a move is taken to be a move of
the b-pawn if one to match the move can be found. Otherwise, Bishop
moves are tried as an alternative. There is no back-up on failure if
picking a valid pawn move was the wrong choice.

Lower-case 'b' as the first character of a Bishop move is not acceptable
in the variations files.

Duplicate detection is not guaranteed to be exact. The -Z flag has
slightly more potential to avoid false duplicates as it compares
separate values for the end position and move sequence, whereas these
are XORed to save space when -Z is not used. However, this will only
make a difference and avoid false matches if two different games at the
same hashtable index also produce identical XORed values.

The results of the -x, -v, and -t/-T search criteria are AND-ed
together. There might be occasions when you wanted to search for games
that matched either positional variations or textual variations at the
same time, for instance. This requires multiple runs of pgn-extract.

The FEN string output with -F does not attempt to record the number of
halfmoves since the last pawn move or capture.

The -Wsan variation that allows selection of the output language is tied
to single-character piece descriptions. This does not support Russian
usage, for instance, in which the King is described as a character pair.


    The Files

The distribution comes with the following files.
COPYING	GNU General Public License
README	A plaintext version of this file.
Makefile	see below.
apply.[ch]	functions concerned with applying moves to a board.
argsfile.[ch]	functions concerned with command line argument processing.
bool.h	Boolean type definition.
decode.[ch]	functions for decoding the text of a move.
defs.h	definitions relating to boards.
eco.[ch]	functions for looking up ECO classifications.
eco.pgn	PGN file of ECO classifications.
end.[ch]	functions for looking for matching endgames.
grammar.[ch]	the parser.
hashing.[ch]	duplicate detection hash tables.
lex.[ch]	the lexical analyser.
lines.[ch]	functions for reading lines.
lists.[ch]	functions for holding the extraction criteria.
map.[ch]	functions for implementing move semantics.
moves.[ch]	functions for collecting moves and variations.
mymalloc.[ch]	functions for memory allocation.
output.[ch]	functions concerned with outputing the games.
taglist.h	constants for tag and pseudo-tag names
tokens.h	type definition for lexical tokens.
typedef.h	type definitions.

The sources include a Makefile for the GNU make program, gmake. I also
use this with the Djgpp gcc compiler for producing the DOS executable
(see Portability <#portability>).


    Portability

pgn-extract is regularly used under DOS (using the Delorie free C
compiler - http://www.delorie.com/djgpp/) Solaris (Gnu C) and various
versions of Linux. I haven't managed to put a Mac version together.


    Acknowledgements

I would like to thank all those who used the program and made
suggestions for things to add. In particular, thanks to Michael Kerry
whose help led to better determination of game boundaries in earlier
versions, and V. Armando Sole whose own filter program was the
inspiration for adding textual variation permutations. John Brogan
suggested adding the ! notation to the variation file and provided the
spur for duplicate detection. He also supplied the original code for
soundex matching (-S). He also provided the code for soundex matching.
Jaroslav Poriz, Ron Leamon, Ed Leonard, Charles Frohman, and Robert
Wilhelm helped with testing at various times. Bernhard Maerz was
instrumental in encouraging the inclusion of ECO classification and
material balance matches, and has provided a large number of ideas for
future versions! He and Peter Otterstaetter suggested the relational
operators in tag files, with Peter also providing the spur to make
duplicate detection work with bigger game files (-Z) and doing some very
useful testing for me. Kayvan Sylvan requested long algebraic output and
identified an error in ECO classification. Cameron Hayne suggested
matching on the number of moves in a game. Owen D. Lyne suggested
extension of the -E flag, and both tested and provided diagnostic data
to help refine the ECO classification aspects of the program.
Karl-Martin Skontorp provided the incentive and testing help that
enabled me to add the -Wepd option. Thanks to all of those people on the
net who provide games in PGN format. Finally, thanks, of course, to
Steven Edwards (sje@mv.mv.com) for his work on developing the PGN standard.


    License

pgn-extract: a Portable Game Notation (PGN) extractor.
This program is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
Free Software Foundation; either version 1, or (at your option) any
later version.

This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
Public License for more details.

You should have received a copy of the GNU General Public License along
with this program; if not, write to the Free Software Foundation, Inc.,
675 Mass Ave, Cambridge, MA 02139, USA.

David Barnes may be contacted as D.J.Barnes@kent.ac.uk
<mailto:d.j.barnes@kent.ac.uk> or via
http://www.cs.kent.ac.uk/people/staff/djb/


    Changes to the Original Release

    * 24th April 2007. Fixed a bug with mate annotation. Added the -M
      flag for checkmate matches, which is due to Richard Jones.
    * 19th October 2005. Added language-specific letters to -Welalg
      following a suggestion from Folkert van Heusden.
    * 1st May 2004: Fixed an error with ECO classification that was
      causing the file list to be out of sync.
    * 29th April 2004: Buffered game text before outputting it, so that
      trailing spaces on lines (which violate the PGN spec) can be deleted.
      Games with zero moves are now acceptable.
    * 26th April 2004: Slight modification to one of the hashing values
      made in order to try to avoid clashes in ECO matches. ECO matches
      now have a discretion of up to 6 half moves.
    * 13th February 2002: Added -Welalg as an output format following a
      suggestion from Rafal Furdzik.
    * 27th March 2001
          o Added output of EPD via -Wepd.
          o Fixed a long standing error in FEN castling rights. These
            were not being withdrawn if a Rook was captured on its home
            square. Pointed out by Karl-Martin Skontorp, who also
            provided the incentive to add -Wepd. 
    * 26th April 2000 Added the -R flag for tag ordering.
    * 22nd April 2000 Completed implementation of -A to work with all
      flags.
    * 21st April 2000
          o Added the -F flag.
          o Added support for reading Russian source files. 
    * 11th April 2000
          o Added the -A flag.
          o Extended usage of -Wsan to support output in different
            languages.
          o Usage of -e with -7 retains an ECO tag in matched games.
          o FEN tags with the -t flag are used as positional matches
            (equivalent to -x matches).
          o Non-standard tags are now retained in game output. 
    * 12th January 2000 C compiler with Red Hat Linux 6 was no longer
      happy with static initialisations involving stdin, stdout and
      stderr. Changes made to lex.c and main.c to work around this.
      Pointed out by Mladen Bestvina.
    * 18th October 1999 Numbers greater than 3 allowed with -E, at the
      request of Owen Lyne.
    * 15th December 1997 Treat \r as WHITESPACE (for DOS files).
    * 8th June 1997 Added -b flag to set bounds on the number of moves
      in a game to be matched.
    * 2nd May 1997 Corrected small error when strings were not
      terminated properly. In tags, this resulted in the corrected tag
      ending in ]"] instead of "].
    * 17th February 1997 Added a little more error recovery.
    * 15th November 1996 Added -Z.
    * 23rd Sep 1996 It is no longer necessary to omit move numbers from
      the variations files (-v and -x). This makes it easier to cut and
      paste games of interest into these files.
    * 28th Jun 1996 It is no longer necessary to terminate the tag file
      (-t). Relational operators added in the tag file (-t). Added -E flag.
    * 7th May 1996 Corrected failure to make ECO classification when
      combined with -x. Added lalg and halg as long algebraic output
      formats.
    * 9th Oct 1995 Add -#
    * 25th Sep 1995: Default to reading stdin if no file arguments are
      provided.
    * 24th Jul 1995: Added setup from FEN tags.
    * 18th Jul 1995:
          o Added material balance matches with -z.
          o Added 'L' as a minor piece letter in ending files. 
    * 14th Jul 1995: Made the order of arguments immaterial.
    * 5th Jul 1995:
          o Added ECO classification with -e.
          o Fixed false partial substring matches with -v, e.g. textual
            variation move Nc6 is now no longer matched by game move c6. 
    * 22nd Mar 1995: Made permutation matching with -v the default and
      added -P to suppress it.
    * Jan 1995: Added -n and -L.
    * 17th Nov 1994: Liberated the program from using YACC and Lex.
    * 13th Oct 1994: Released test version with ChessMaster output.
    * 20th Sep 1994: Added move rewriting and -W flag.
    * 7th Sep 1994: Added -D flag.
    * 6th Sep 1994: Added -C and -V flags and soundex matching.
    * 5th Sep 1994:
          o Integrated the positional variation code from a separately
            developed program.
          o Added -N flag.
          o Added ! to the textual variation syntax.
          o Removed the writing to extract.pgn that was present in an
            earlier unreleased version.
          o Added -d flag. 
    * 8th Jul 1994:
          o Added -o flag.
          o Discarded writing to standard output in DOS version because
            of extensive problems trying to make this work with
            redirected output. Instead, output is written to the file
            extract.pgn. 
    * 6th Jul 1994: Added -7 flag.
    * 9th May 1994: Added -p flag for variation permutations.
    * 6th May 1994: Added * as a don't-care move in variations files.
    * 26th Apr 1994: Added the -t flag for files of extraction criteria.
    * 25th Apr 1994: Added the -T flag for extraction criteria.
    * 22nd Apr 1994: Added the -f flag for handling lists of PGN files.
    * 13th Apr 1994:
          o Cleaned up the game-length determination by reading/writing
            files in binary-mode.
          o Added -a flag for appending to existing .pgn files.
          o Added multiple input files.
          o Made verbose output the default behaviour. 

------------------------------------------------------------------------
Copyright (C) 1994-2007 David Barnes
D.J.Barnes@kent.ac.uk <mailto:d.j.barnes@kent.ac.uk>
Date of this version: 24th April 2007
Version Number: 16.2

