link-parser - parses natural language sentences
link-parser [language] [-pp pp_knowledge_file] [-c
constituent_knowledge_file] [-a affix_file] [-ppoff] [-coff] [-aoff]
[-batch] [-<special "!" command>]
In Selator, D. and Temperly, D. "Parsing English with a Link Grammar"
(1991), the authors defined a new formal grammatical system called a
"link grammar". A sequence of words is in the language of a link
grammar if there is a way to draw "links" between words in such a way
that the local requirements of each word are satisfied, the links do
not cross, and the words form a consistent connected graph. The authors
encoded English grammar into such a system, and wrote link-parser to
parse English using this grammar.
This package can be used for linguistic parsing for information
retrieval or extraction from natural language documents. Abiword also
uses it as a grammar checker.
-<special ! command>
link-parser, when invoked manually, will take control of the terminal;
link-parser will then attempt to analyze the grammar of all input,
unless escaped with an exclamation mark, according to the dictionary
file provided as an argument. If escaped, the input will be treated as
a "special command"; "!help" lists all special commands available.
link-parser depends on a link-grammar dictionary which contains lists
of words and associated metadata about their grammatical properties in
order to analyze sentences. A link-grammar dictionary provided by the
authors of link-grammar is usually included with the link-grammar
package, and can often be found somewhere in the
/usr/share/link-grammar/ hierarchy. When this is the case, only the
two-letter language code needs to be specified on the command-line.
Alternatively, a user can provide their own dictionary as an argument,
in which case the dictionary’s directory should be specified. Hence,
either of the commands
will run link-parser using the english dictionary included with
While in a link-parser session, some example output could be:
linkparser> Reading a man page is informative.
++++Time 0.00 seconds
Found 1 linkage (1 had no P.P. violations)
Unique linkage, cost vector = (UNUSED=0 DIS=0 AND=0 LEN=12)
| +---------Ss*g---------+ |
| +-------Os-------+ | |
| | +----Ds----+ | |
+----Wd---+ | +--AN--+ +---Pa---+ |
| | | | | | | |
LEFT-WALL reading.g a man.n page.n is.v informative.a .
A P.P. violation is a post-processing violation; it is a post-linkage
step used to reject invalid parses. The link types shown are specific
to English; other langauges will have different link types.
link-parser can also be used non-interactively, either through its API,
or via the -batch option. When used with the -batch option,
link-parser passively receives input from standard input, and when the
stream finishes, it then outputs its analysis. So one could construct
an ad-hoc grammar checker by piping text through link-parser with a
batch option, and seeing what sentences fail to parse as valid:
cat thesis.txt | link-parser /usr/share/link-grammar/en/4.0.dict
Information on the shared-library API and the link types used in the
parse is avavailable at the Abiword website at
Peer-reviewed papers explaining link-parser can be found at the
original CMU site at http://www.link.cs.cmu.edu/link/papers/index.html.
link-parser was written by Daniel Sleator <firstname.lastname@example.org>, Davy
Temperley <email@example.com>, and John Lafferty
This manual page was written by Ken Bloom <firstname.lastname@example.org>, for the
Debian project (but may be used by others).
April 18, 2008 LINK-GRAMMAR(1)