NAME

Lingua::Treebank - Perl extension for manipulating the Penn Treebank format

SYNOPSIS

  use Lingua::Treebank;

  my @utterances = Lingua::Treebank->from_penn_file($filename);

  foreach (@utterances) {
    # $_ is a Lingua::Treebank::Const now

    foreach ($_->get_all_terminals) {
      # $_ is a Lingua::Treebank::Const that is a terminal (word)

      print $_->word(), ' ' $_->tag(), "\n";
          }

    print "\n\n";

  }

ABSTRACT

  Modules for abstracting out the "natural" objects in the Penn
  Treebank format.

DESCRIPTION

This class knows how to read two treebank formats, the Penn format and the Chomsky Normal Form (CNF) format. These formats differ in how they handle terminal nodes. The Penn format places pre-terminal part of speech tags in the left-hand position of a parenthesis-delimited pair, just like it does non-terminal nodes. The CNF format attaches pre-terminal tags to the word with an underscore. For example, the sentence "I spoke" would be rendered in each format as follows:

    (S
        (NP
            (N I))
        (VP
            (V spoke)))
            Penn

    (S
        (NP
            I_N)
        (VP
            spoke_V))
     Chomsky Normal Form

Almost all the interesting tree-functionality is in the constituent-forming package (included in this distribution, see the Lingua::Treebank::Const manpage).

PLEASE NOTE: The format expected here is the .mrg format, not the .psd format. In other words, one POS-tag per word is required. (In response to CPAN bug 15079.)

Variables

CONST_CLASS

The value Lingua::Treebank::CONST_CLASS indicates what class should be used as the class for constituents. The default is Lingua::Treebank::Const; it will generate an error to use a value for $Lingua::Treebank::CONST_CLASS that is not a subclass of Lingua::Treebank::Const.

Methods

Class methods

from_penn_file

given a Penn treebank file, open it, extract the constituents, and return the roots.

from_penn_fh

given a Penn treebank filehandle, extract the constituents and return the roots.

from_cnf_file

given a Chomsky normal form file, open it, extract the constituents, and return the roots.

from_cnf_fh

given a Chomsky normal form filehandle, extract the constituents and return the roots.

EXPORT

None by default.

HISTORY

1. 01

   Original version; created by h2xs 1.22 with options

     -CAX
           Lingua::Treebank

2. 02

   Improved documentation.

3. 03

   added a VERBOSE variable that can be set.

4. 09

   A variety of additional features

5. 10

   more features still, also some bugfixes.

6. 11

   Removed references to Text::Balanced, which is slow and not uniformly available.

7. 12

   Corrected bug in Makefile.PL pointed out by Vassilii Khachaturov.

   Added some documentation distinguishing that .mrg (and not .psd files) are supported.

8. 13

   text() method now suppresses anything with a -NONE- tag.

   $VERSION for the Lingua::Treebank manpage and the Lingua::Treebank::Const manpage now tied.

9. 14

   Actually include patch intended for 0.13. *sheesh*.

SEE ALSO

TO DO: mention documentation of Penn Treebank

AUTHOR

Jeremy Gillmor Kahn, <kahn@cpan.org>

COPYRIGHT AND LICENSE

Copyright 2003-2005 by Jeremy Gillmor Kahn with additional support from Bill McNeill

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.