Link grammar

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Link grammar (LG) is a theory of syntax by Davy Temperley and Daniel Sleator which builds relations between pairs of words, rather than constructing constituents in a tree-like hierarchy. There are two basic parameters: directionality and distance. Link grammar is similar to dependency grammar, but dependency grammar includes a head-dependent relationship, as well as lacking directionality in the relations between words. Colored Multiplanar Link Grammar (CMLG) is an extension of LG allowing crossing relations between pairs of words[1]




Rightward links are represented as a +, and leftward links with a . Optional links are contained in curly brackets {}. Undesirable links are contained in any number of square brackets []. Multiple links are joined either by a conjunction & or a disjunction or. Each rule ends with a semicolon ;.


Example 1[edit]

A basic rule file for an SVO language might look like:

<determiner>:      D+;
<verb>:               S−   &   {O+};


 |   |     |     |     |
The boy painted  a  picture

Example 2[edit]


<noun-subject>:   S+;
<noun-object>:     O+;


 |     +--O--+
 |     |     |
man   nAn xordam


The link grammar syntax parser is a library for natural language processing written in C. It is available under the BSD license, which is compatible with the GNU General Public License. The parser[2] is an ongoing project. Recent versions include improved sentence coverage, various bug and security fixes, and Java language bindings.

There are also Perl, Python, Ruby, OCaml and .NET bindings available.[3]

The link-grammar program along with rules and word lists for English may be found in standard Linux distributions, e.g., as a Debian package.[4]


AbiWord checks grammar using Link Grammar



Link Grammar has also been employed for information extraction of biomedical texts[9][10] and events described in news articles,[11] as well as experimental machine translation systems from English to German and Turkish.

The Link Grammar link dictionary is used to generate and verify the syntactic correctness of two different natural language generation systems: NLGen[12] and NLGen2.[13] It is also used as a part of the NLP pipeline in the OpenCog AI project.


  1. ^ .Anssi Yli-Jyrä and Matti Nykänen (2004). "A Hierarchy of Mildly Context-Sensitive Dependency Grammars". In G. P. Gerhard Jäger, Paola Monachesi and S. Wintner. Proceedings of the 9th conference on Formal Grammar 2004 "FGNancy". Pre-Proceedings. pp. 151–165. 
  2. ^ AbiWord — Link Grammar Parser
  3. ^ (Perl) (Python) (Ruby) (OCaml) (.NET)
  4. ^ Debian - Package Search Results - link-grammar
  5. ^ AbiWord — Link Grammar Parser
  6. ^ RelEx Dependency Relationship Extractor
  7. ^ The Stanford Parser: A statistical parser
  8. ^ The Penn Treebank Project
  9. ^ Jing Ding, Daniel Berleant, Jun Xu, Andy W. Fulmer (November 2003). "Extracting biochemical interactions from MEDLINE using a link grammar parser". Tools with Artificial Intelligence, 2003. Proceedings. 15th IEEE International Conference on. pp. 467–471. ISBN 0-7695-2038-3. 
  11. ^ Harsha V. Madhyastha, N. Balakrishnan, K. R. Ramakrishnan (2003). "Event Information Extraction Using Link Grammar". 13th International WorkShop on Research Issues in Data Engineering: Multi-lingual Information Management (RIDE'03). p. 16. doi:10.1109/RIDE.2003.1249841. 

Further reading[edit]

External links[edit]

Language extensions[edit]