=head1 NAME
TODO Things to do in the Ngram Statistics Package
=head1 SYNOPSIS
Ngram Statistics Package Todo list
=head1 DESCRIPTION
The following list describes some of the features that we'd like to
include in NSP in future. No particular priority is assigned to these
items - they are all things we've discussed amongst ourselves or with
users and agree would be good to add.
If you have additional ideas, or would like to comment on something on the
current list, please let us know via the ngram mailing list.
=head2 WEB INTERFACE / WEB SERVER
It would be nice to offer a web interface or web server for users who
just want to run a few measures.
=head2 UNICODE SUPPORT / ENCODING ISSUES
NSP is geared for the Roman alphabet (Latin-1). Perl has increasingly
better Unicode support with each passing release, and we will
incorporate Unicode support in future. We attempted to use the Unicode
features in Perl 5.6, but found them to be incomplete. We have not yet
attempted this with Perl 5.8 (the now current version) but it is said to
be considerably better.
Perl support for unicode will include language / alphabet specific
definitions of regular expression character classes like \d+ or \w+
(digits and non-white space characters). So you should be able to use
(in theory) the same regular expression definitions with any alphabet
and have it match in a way that makes sense for that language.
Our expertise in this area is fairly limited, so please let us know if
we are missing something obvious or misunderstanding what Perl is
attempting to do.
In a discussion in Feb 2008, Richard Jelinek suggested the use of the
ENCODE module, discussion starts here :
L<http://tech.groups.yahoo.com/group/ngram/message/210>
In that discussion some drawbacks to 'use locale' were pointed out, so
for the moment we have made no changes, but it seems like fitting NSP
with ENCODE support is a good idea.
=head2 MORE EFFICIENT COUNTING
Right now all the ngrams being counted are stored in memory. Each ngram is
an element in a hash. This is ok for up to a few million word corpora,
but after that things really slow down. We would like to pursue the idea
of using suffix trees which would greatly improve space utilization.
The use of suffix trees for counting term frequencies is based on :
Yamamoto, M. and Church, K (2001) Using Suffix Arrays to compute Term
Frequency and Document Frequency for All Substrings in a Corpus,
Computational Linguistics, vol 27:1, pp. 1-30, MIT Press.
Find the article at:
L<http://acl.ldc.upenn.edu/J/J01/J01-1001.pdf>
L<http://www.research.att.com/~kwc/CL_suffix_array.pdf>
In fact, they even provide a C implementation:
L<http://www.milab.is.tsukuba.ac.jp/~myama/tfdf/index.html>
However, we would convert this into Perl and may need to modify it
somewhat to fit into NSP.
Another alternative would be to simply modify the count.pl program such
that rather than using memory it used disk space to accumulate counts.
This would be very slow but might suffice for certain situations. This
is what huge-count.pl currently does.
Another alternative would be to tie the hashes that are used in NSP to
a database, and thereby reduce some memory use.
Regardless of the changes we make to counting, would continue to support
counting in memory, which is perfectly adequate for smaller amounts of
corpora.
=head2 GET COUNTS FROM WEB
The web is a huge source of text, and we could get counts for words
or ngrams from the web (probably using something like Perl LWP module).
Rather than running count.pl on a particular body of text (as is the case
now) we'd probably have to run count.pl such that it looked for counts for
a specific set of words as found on the web. Simply running count.pl on
the entire www wouldn't really make sense. So perhaps we would run count
on one sample to get a list of the word types/ngrams that we are
interested in, and then run count on the www to find out their
respective counts.
[Our interest in this has been inspired by both Peter Turney (ACL-02
paper) and Frank Keller (EMNLP-02 paper).]
=head2 PARALLEL COUNTING
Counting words and ngrams in large corpora could be parallelized. The
trick is not so much in the counting, but in the combining of counts
from various sources.
This is something we might try and implement using MPI (Message Passing
Interface).
=head2 PROGRESS METER for count.pl
When processing large files, count.pl gives no indication of how much of
the file has been processed, or even if it is still making progress. A
"progress meter" could show how much of the file has been proceeded, or
how many ngrams have been counted, or something to indicate that progress
is being made.
=head2 OVERLY LONG LINE DETECTOR for count.pl
If count.pl encounters a very long line of text (with literally thousands
and thousands of words on a single line) it may operate very very slowly.
It would be good to let a user know that an overly long line (we'd
need to define more precisely what "overly long" is) is being processed
(this fits into the progress meter mentioned above) so that a user can
decide if they want to continue with this, or possibly terminate
processing and reformat the input file.
=head2 GENERALIZE --newLine in count.pl
The --newLine switch tells count.pl that Ngrams may not cross over end of
line markers. Presumably this would be used when each line of text
consists of a sentence (thus the end of a line also marks the end of
a sentence). However, if the text is not formatted and there may be
multiple sentences per line, or sentences may extend across several lines,
we may want to allow --newLine to include other characters that Ngrams
would not be allowed to cross.
For example we could have the switch --dontCross "\n\.,;\?" which would
prevent ngrams from crossing the newline, the fullstop, the comma, the
semicolon and the question mark.
=head2 RECURSE LIKE OPTION THAT CREATES MULTIPLE COUNT FILES
Our current --recurse option creates a single count output file for
all the words in all the texts found in a directory structure. We might
want to be able to process all the files in a directory structure such
that each file is treated separately and a separate count file is
created for it.
For example, suppose we have the directory /txts that contains the
files text1 and text2.
count.pl --recurse output txts
output will consist of the combined counts from txts/text1 and txts/text2.
This new option would count these files separately and produce separate
count output files.
=head2 OTHER CUTOFFS FOR count.pl
DONE IN VERSION 1.13! (--uremove option): What about having a frequency
cutoff for count.pl that removed any ngrams that occur more than some
number of times? The idea here would be to eliminate high frequency
ngrams not through the use of a stoplist but rather through a frequency
cutoff, based on the presumption that most very high frequent ngrams
will be made up of stop words.
What about a percentage cutoff? In other words, eliminate the least (or
most) frequent ngrams?
=head2 AUTOMATIC CREATION OF STOPLISTS
It would be useful to allow NSP to automatically create a stoplist based
on a combination of frequency counts and/or scores like tf/idf. While
tf/idf depends on the idea of a document, we would simply chunk up a
large corpus into 100 token long pieces, and consider each piece a
document, and consider stop words those words that occur in some number of
these chunks.
=head2 SUPPORT FOR STDIN/STDOUT
Right now count.pl and statistic.pl operate such that the output file
is designated first, followed by the input file.
For example,
count.pl outputfile inputfile
However, there are advantages to allowing a user to redirect input
and output, particularly in the Unix and MS-DOS world. As Derek Jones
pointed out to us, if we have Windows users they are probably looking
for a GUI (and they won't find much will they!!). This would enable the
use of syntax such as...
count.pl input > out
cat input | count.pl > outfile
which would help in building scripts, etc.
=head2 INSTALL SCRIPT FOR UNIX
Rather than have user set paths, have a script that would ask the users
questions to set things up properly. This might be especially useful if
we want to maintain the "old" style of output input file specifications in
count.pl and statistic.pl (see point above) as well as STDIN STDOUT.
(Maybe a user could pick which one?) In addition, there may be other
options that a user could specify this way (such as a default token
definition, home directory, etc.)
=head2 EXTEND huge-count.pl to Ngrams
At present huge-count.pl is only able to count bigrams. It would be very
useful to extend it so that it could count Ngrams in general. Also, there
is no support for windowing provided at present, so the bigrams it counts
must be adjacent. It would be desirable to support windowing for bigrams
and Ngrams generally.
=head2 ERROR RETURN CODES
At present all programs simply exit when they encounter an error. We will
return an error code that can be detected by the calling program, so that
abnormal termination is clear. This affects count.pl and statistic.pl
particularly, but will also be changed in rank.pl, combig.pl and kocos.pl.
=head2 MODULAR COUNTING
There is a certain amount of redundant code in count.pl, huge-count.pl and
kocos.pl. It would be useful to make these more modular, to allow for
inheritance and code sharing, as well as the use of objects (potentially).
=head2 RANK.PL TIE HANDLING
Right now rank.pl does not handle ties in any way other than re-ranking
them such that all members of a tie have the same rank, and that the
next rank after the ties is incremented by the number of ties. Some
sources advocate using Pearson's correlation coefficient on the ranks in
case of ties :
L<http://en.wikipedia.org/wiki/Spearman%27s_rank_correlation_coefficient>
Other sources prefer the use of Kendall's Tau over Spearman's:
L<http://rsscse.org.uk/ts/bts/noether/text.html>
Our suggestion is that if you have data with numerous ties, you want to
look very carefully at alternatives to the methods described in rank.pl
However, typical collocation data collected from corpora usually doesn't
have too many ties, so in general we feel rank.pl remains useful.
=head2 UPDATE USAGE.pod
USAGE.pod has not been updated since 2001, and is very basic.
=head1 AUTHOR
Ted Pedersen, tpederse@d.umn.edu
Last Updated : $Id: TODO.pod,v 1.6 2010/03/04 04:08:16 tpederse Exp $
=head1 BUGS
=head1 SEE ALSO
home page: L<http://www.d.umn.edu/~tpederse/nsp.html>
mailing list: L<http://groups.yahoo.com/group/ngram/>
=head1 COPYRIGHT
Copyright (C) 2000-2010 Ted Pedersen
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Note: a copy of the GNU Free Documentation License is available on the web
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