Link Grammar

Davy Temperley    Daniel Sleator    John Lafferty

The Link Grammar Parser is a syntactic parser of English, based on link grammar, an original theory of English syntax. Given a sentence, the system assigns to it a syntactic structure, which consists of a set of labeled links connecting pairs of words. The parser also produces a "constituent" representation of a sentence (showing noun phrases, verb phrases, etc.).

We have made the entire system available for download on the web. The system is written in generic C code, and runs on any platform with a C compiler. There is an application program interface (API) to make it easy to incorporate the parser into other applications.

As of December 2004, we are releasing the parser under a new license; the license allows unrestricted use in commercial applications, and is also compatible with the GNU GPL (General Public License). You can view the license here. We are also releasing version 4.1b, which is identical to version 4.1 (released in 2000) except that the licensing statements reflect the new license.

The parser has a dictionary of about 60000 word forms. It has coverage of a wide variety of syntactic constructions, including many rare and idiomatic ones. The parser is robust; it is able to skip over portions of the sentence that it cannot understand, and assign some structure to the rest of the sentence. It is able to handle unknown vocabulary, and make intelligent guesses from context and spelling about the syntactic categories of unknown words. It has knowledge of capitalization, numerical expressions, and a variety of punctuation symbols.

The parser is now being maintained under the auspices of the Abiword project. The latest versions include new features and many improvements. For more information, go to the Abiword link grammar page.

Here is the contents of this site:
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Parse Experiment with the parser.
Translator Experiment with the Link Grammar English-To-German Translator--a simple translation system which demonstrates one approach to using Link Grammar for translation. (No longer supported)
Samples A list of 900 sample sentences illustrates the range of phenomena of English grammar captured by our system.
Documentation An introduction to link grammars and the Link Parser 4.0; detailed documentation of the current dictionary; documentation of the Link Parser API, for installing the link parser into your own programs.
Bibliography A collection of papers about link grammar.
Improvements Improvements in Version 4.0.
Palindromes A list of short palindromes generated by the system.
Download Download all the source and data files for the link grammar parser here.

If you have any comments about this work, or are using it for your own purposes, we would like to hear from you. You can send us electronic mail.


The research described here was supported by NSF, ARPA, and the School of Computer Science, at Carnegie Mellon University. Special thanks to Adam Berger for developing the post-processing system, and to Dennis Grinberg for contributions to the null-link system.

John Lafferty     Daniel Sleator     Davy Temperley

Daniel Sleator
Last modified: Sat Apr 2 23:46:55 EDT 2016