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Constraint Grammar

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Constraint Grammar is a tool that can be used to POS-tag ambiguous text. There are free constraint grammars developed outside the Apertium project for: Norwegian (the Oslo-Bergen tagger), Sámi languages (from Giellatekno), Faroese (also from Giellatekno), Finnish (by Fred Karlsson).

[edit] Terminology

See also: Apertium stream format
Apertium equivalent: ^words/word<n><pl>/word<vblex><pres><p3><sg>$
  • baseform — the lemma of a word.
  • reading — a single analysis of a word.
Apertium equivalent: ^word<n><pl>$

[edit] Note on parenthesis

The use of parentheses to distinguish between tags and lists/sets seems to be the main confusing point for people learning CG. If we have the morphological tags tag1 and tag2, then we can have rules like this:

LIST set1 = tag1 ;
LIST set2 = (tag1 tag2) ; # matches a word with both tag1 and tag2
LIST set3 = tag1 tag2 ;   # matches a word with tag1 or tag2
LIST word = "hello" ;

SELECT:1a (tag1) (1 word) ;
SELECT:1b  set1  (1 word) ;   # equivalent to 1a

SELECT:2a (tag1 tag2) (1 word) ;
SELECT:2b  set2       (1 word) ;   # equivalent to 2a

SELECT:3a tag1 (1 word) ;
SELECT:3b tag2 (1 word) ;
SELECT:3c set3 (1 word) ;   # equivalent to 3a and 3b combined

SELECT:1c  set1  (1 ("hello")) ; # equivalent to 1a (or 1b)

[edit] Languages using CG in Apertium

and many others. The following languages currently (2014-06-27) have CG's of over 100 rules:

[edit] When is CG needed?

Currently some of the CG rules written in the above language pairs may be written as forbid rules in the TSX format used by apertium-tagger. If the rules for your language pair can be written in the .tsx format, you can go for an easier design without a CG module in that language pair.

[edit] See also

[edit] External links

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