1LINK-PARSER(1)              General Commands Manual             LINK-PARSER(1)
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NAME

6       link-parser - parse natural language sentences using Link Grammar
7

SYNOPSIS

9       link-parser --help
10       link-parser --version
11       link-parser [language|dict_location] [-<special_"!"_command>...]
12

DESCRIPTION

14       link-parser  is  the  command-line  wrapper to the link-grammar natural
15       language parsing library.  This library  will  parse  English  language
16       sentences,  generating  linkage trees showing relationships between the
17       subject, the verb, and various adjectives, adverbs, etc.  in  the  sen‐
18       tence.
19

EXAMPLE

21       link-parser
22
23       Starts the parser interactive shell.  Enter any sentence to parse:
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25       linkparser> Reading a man page is informative.
26
27       Found 12 linkages (12 had no P.P. violations)
28            Linkage 1, cost vector = (UNUSED=0 DIS= 0.20 LEN=16)
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30           +------------------------Xp------------------------+
31           +--------------->WV-------------->+                |
32           |         +----------Ss*g---------+                |
33           |         +--------Os-------+     |                |
34           |         |     +---Ds**x---+     |                |
35           +----Wd---+     |    +---A--+     +---Pa---+       |
36           |         |     |    |      |     |        |       |
37       LEFT-WALL reading.g a man.ij page.n is.v informative.a .
38

BACKGROUND

40       The link-parser command-line tool is useful for general exploration and
41       use, although it is presumed that, for the parsing of large  quantities
42       of  text, a custom application, making use of the link-grammar library,
43       will be written.  Several such applications are described on  the  Link
44       Grammar  web page (see SEE ALSO below); these include the AbiWord gram‐
45       mar checker, and the RelEx semantic relation extractor.
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47       The theory of Link Grammar is explained in many  academic  papers.   In
48       the first of these, Daniel Sleator and Davy Temperley, "Parsing English
49       with a Link Grammar" (1991), the authors defined a new formal grammati‐
50       cal  system called a "link grammar". A sequence of words is in the lan‐
51       guage of a link grammar if there is a way to draw "links" between words
52       in  such  a way that the local requirements of each word are satisfied,
53       the links do not cross, and  the  words  form  a  consistent  connected
54       graph.  The  authors  encoded  English  grammar into such a system, and
55       wrote link-parser to parse English using this grammar.
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57       The engine that performs the parsing is separate from the  dictionaries
58       describing  a  language.  Currently, the most fully developed, complete
59       dictionaries are for the English and Russian languages, although exper‐
60       imental,  incomplete  dictionaries  exist for German, and several other
61       languages.
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63

OVERVIEW

65       link-parser, when invoked manually, starts an interactive shell, taking
66       control  of the terminal.  Any lines beginning with an exclamation mark
67       are assumed to be a "special command"; these are described below.   The
68       command !help will provide more info; the command !variables will print
69       all of the special commands.  These are  also  called  "variables",  as
70       almost all commands have a value associated with them: the command typ‐
71       ically enable or disable some function, or they alter some multi-valued
72       setting.
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74       All  other  input is treated as a single, English-language sentence; it
75       is parsed, and the result of the parse is printed.  The variables  con‐
76       trol  what  is  printed:   By  default,  an  ASCII-graphics  linkage is
77       printed, although post-script output is also possible.  The printing of
78       the constituent tree can also be enabled. Other output controls include
79       the printing of disjuncts, complete link data, and word senses.
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81       In order to analyze sentences, link-parser depends  on  a  link-grammar
82       dictionary.  This contains lists of words and associated metadata about
83       their grammatical properties.  An English language dictionary  is  pro‐
84       vided  by default.  If other language dictionaries are installed in the
85       default search locations, these may be explicitly specified by means of
86       a 2-letter ISO language code: so, for example:
87
88           link-parser de
89
90       will start the parser shell with the German dictionary.
91
92       Alternately,  the  dictionary location can be specified explicitly with
93       either an absolute or a relative file path; so, for example:
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95           link-parser /usr/share/link-grammar/en
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97       will run link-parser using the English dictionary located in the  typi‐
98       cal install directory.
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100       link-parser can also be used non-interactively, either through its API,
101       or  via  the  -batch  option.   When  used  with  the  -batch   option,
102       link-parser  reads  from  standard input, generating output to standard
103       out. So, for example:
104
105           cat thesis.txt | link-parser -batch
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107       Note that using the -batch option  disables  the  usual  ASCII-graphics
108       linkage  printing.   This may be re-enabled via a special command; spe‐
109       cial commands may be interspersed with the input.
110
111       Alternately, an input file may be specified with the !file special com‐
112       mand, described below.
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114

OPTIONS

116       --help Print usage and exit.
117
118       --version
119              Print version number and exit.
120
121
122   Special ! options
123       The special "!" options can be specified either on the command-line, on
124       startup, or set and toggled within the interactive shell  itself.   The
125       full  option name does not need to be used; only enough letters to make
126       the option unique must be specified.
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128       Boolean variables may be toggled simply by  giving  the  !varname,  for
129       example, !batch.  Setting other variables require using an equals sign:
130       !varname=value, for example, !width=100.
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132       The !help command will print general help, and the  !variables  command
133       will  print  all  of  the current variable settings.  The !file command
134       will read input from a file.  The !file command is not a  variable;  it
135       cannot be set.  It can be used repeatedly.
136
137       The !exit command will cause link-parser to exit.
138
139       The  dictionary  entry  for  any given word (optionally terminated by a
140       subscript) may be examined by preceding it with two exclamation  marks.
141       A  wildcard character '*' can be specified as the last character of the
142       word in order to find multiple matches.
143
144       Default values of the options below are shown in parenthesis.  Most  of
145       them are the default ones of the link-grammar library.  Boolean default
146       values are shown as on (1) or off (0).
147
148       -bad (off)
149              Enable display of bad linkages.
150
151       -batch (off)
152              Enable batch mode.
153
154       -cluster (off)
155              Use clusters to loosen parsing.
156
157       -constituents (0)
158              Generate constituent output. Its value may be:
159
160              0      Disabled
161
162              1      Treebank-style constituent tree
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164              2      Flat, bracketed tree [A like [B this B] A]
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166              3      Flat, treebank-style tree (A like (B this))
167
168       -cost-max (2.7)
169              Largest cost to be considered.
170
171       -disjuncts (off)
172              Display of disjuncts used.
173
174       -echo (off)
175              Echo input sentence.
176
177       -graphics (on)
178              Enable graphical display of linkage.  For each linkage, the sen‐
179              tence  is  printed  along with a graphical representation of its
180              linkage above it.
181
182              The following notations are used for words in the sentence:
183
184              [word] A word with no linkage.
185
186              word[?].x
187                     An unknown word whose POS category x has  been  found  by
188                     the parser.
189
190              word[!]
191                     An  unknown  word whose link-grammar dictionary entry has
192                     been assigned by a RegEx.  (Use !morphology=1 to see  the
193                     said dictionary entry.)
194
195              word[~]
196                     There  was  an  unknown word in this position, and it has
197                     got replaced, using a spell guess with this word, that is
198                     found in the link-grammar dictionary.
199
200              word[&]
201                     This  word  is  a  part of an unknown word which has been
202                     found to consist of two or more words  that  are  in  the
203                     link-grammar dictionary.
204
205       -islands-ok (on)
206              Use null-linked islands.
207
208       -limit (1000)
209              Limit the maximum linkages processed.
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211       -links (off)
212              Enable display of complete link data.
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214       -null (on)
215              Allow null links.
216
217       -morphology (off)
218              Display  word morphology.  When a word matches a RegEx, show the
219              matching dictionary entry.
220
221       -panic (on)
222              Use "panic mode" if a parse cannot be quickly found.
223
224       -postscript (off)
225              Generate postscript output.
226
227       -senses (off)
228              Display word senses.
229
230       -short (16)
231              Maximum length of short links.
232
233       -spell (7)
234              If zero, no spell and run-on corrections of  unknown  words  are
235              performed.
236              Else,  use  up  to  this many spell-guesses per unknown word. In
237              that case, the number of  run-on  corrections  (word  split)  of
238              unknown words is not limited.
239
240       -timeout (30)
241              Abort parsing after this many seconds.
242
243       -use-sat (off)
244              Use Boolean SAT-based parser.
245
246       -verbosity (1)
247              Level of detail in output.
248
249       -walls (off)
250              Display wall words.
251
252       -width (16381)(*)
253              The width of the display.
254              * When writing to a terminal, this value is set from its width.
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256

FILES

258       The  following files are per-language, when LL is the 2-letter ISO lan‐
259       guage code.
260
261       LL/4.0.dict
262              The Link Grammar dictionary.
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264       LL/4.0.affix
265              Values of entities used in tokenization.
266
267       LL/4.0.regex
268              Regular expressions (see regex(7)) that are used to match tokens
269              not found in the dictionary.
270
271       LL/4.0.knowledge
272              Post-processing definitions.
273
274       LL/4.0.constituent-knowledge
275              Definitions for producing a constituent tree.
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277
278
279       The directory search order for these files is:
280              ./
281              data/
282              ../
283              ../data/
284              A custom path, as set by the API call dictionary_set_data_dir().
285              /usr/share/link-grammar/
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287

SEE ALSO

289       Information  on  the link-grammar shared-library API and the link types
290       used   in   the   parse   is   available   at   the   AbiWord   website
291http://www.abisource.com/projects/link-grammar/⟩.
292
293       Peer-reviewed  papers  explaining Link Grammar can be found at original
294       CMU site ⟨http://www.link.cs.cmu.edu/link/papers⟩.
295
296       The source code of link-parser and the link-grammar library is  located
297       at GitHub ⟨https://github.com/opencog/link-grammar⟩.
298
299       The  mailing list for Link Grammar discussion is at link-grammar Google
300       group ⟨http://groups.google.com/group/link-grammar?hl=en⟩.
301

AUTHOR

303       link-parser and the link-grammar library were written by Daniel Sleator
304       <sleator@cs.cmu.edu>,  Davy Temperley <dtemp@theory.esm.rochester.edu>,
305       and John Lafferty <lafferty@cs.cmu.edu>
306
307       This manual page was written by Ken Bloom <kbloom@gmail.com>,  for  the
308       Debian project, and updated by Linas Vepstas <linasvepstas@gmail.com>.
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312Version 5.3.8                     2016-06-29                    LINK-PARSER(1)
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