Link Grammar

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A Link Grammar is a Natural Language Grammar based on manually created rules about what type of Words must precede or follow a given Word.

  • Context:
    • Originally developed in the early 1990s by Sleator et al.
    • Has resulted in several applications; but has not been extended since its initial inception.
    • It is a highly lexicalized grammar, so one of the main constraints to its general application is its requirement of an extensive dictionary of words and the production rules associated with each.
    • It is not formally associated to a Natural Language Syntactic Theory, but is suggested to be most similar to a Dependency Grammar.
    • Has been proven to be a Context Free Grammar.
    • “A sequence of words is a sentence of the language defined by the grammar if there exists a way to draw links among the words so as to satisfy the following conditions:
    • Planarity: The links do not cross (...)
    • Connectivity: The links suffice to connect all the words of the sequence together.
    • Satisfaction: The links satisfy the linking requirements of each word in the sequence.
    • The linking requirements of each word are contained in a dictionary. (Sleator & Temperley 1993: 1)
    • Links are typed. A current set of types are summarized at: http://www.link.cs.cmu.edu/link/dict/summarize-links.html . The links include:
      • S: connects subject nouns to finite verbs: "The DOG CHASED the cat": "The DOG [IS chasing / HAS chased / WILL chase] the cat".
      • EB: connects adverbs to forms of "be" before an object or prepositional phrase: "He IS APPARENTLY a good programmer".
      • P: connects forms of the verb "be" to various words that can be its complements: prepositions, adjectives, and passive and progressive participles: "He WAS [ANGRY / IN the yard / CHOSEN / RUNNING ]”.
  • Example(s):
    • +-----Jp-----+

+--Ss-+---Paf-+--MVp--+ +--Dmc--+ | | | | | | Mozart was(v) great(a) among the composers(n).

References

  • http://hyper.link.cs.cmu.edu/link/
  • tbd
    • 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.).
  • tbd
    • “The syntactic analysis uses the robust dependency-based parser Link Grammar (LG) [16], which is able to handle a wide range of syntactic structures [17]. Syntactically unresolvable ambiguities, such as prepositional phrase attachment or gerund and infinitive constructions, are treated with a corpus-based approach (1994_RuleBasedPPDisambiguation)
    • “LG uses linkages to describe the syntactic structure of a sentence (see figure 2). Links connect pairs of words in such a way that the requirements of each word described in the sentences are satisfied, that the links do not cross, and that the words form a connected graph. Despite some extensions at the lexical and syntactic level, processing the frequent occurrences of multi-word, domain specific terminology proved problematic for LG. The addition of a new module, capable of identifying these previously detected terms, ensures they are parsed as single syntactic units. This reduces the complexity of parsing the AMM, by as much as 50%. Also, the output of LG has been extended to include the direction of the linkages as this information is vital for anaphora resolution and semantic analysis.
    • “As LG returns all possible parses, it is necessary to disambiguate among them [13]. The two possibilities for the prepositional phrase attachment returned in figure 2, will be reduced to (b) by the disambiguator as this linkage correctly identifies the dependency relations. The link Wd connects the subject coax cable to the wall. The wall functions as a dummy word at the beginning of every sentence and has linking requirements like any other word. Ss links the transitive verb connects with the subject on the left, the verbal head on the right. The transitive verb and its direct object external antenna, that acts as the head of a noun phrase, are connected by the Os link. MVp connects the verb to the modifying prepositional phrase. Finally, the link Js connects the preposition to with its object ANT connection.
    • “These dependency relations are used to generate the semantic representation of the sentence. LG has a robust component, parsing complex or ungrammatical structures, so that ExtrAns may still produce MLFs, extended with special predicates that mark the unprocessed words as “keywords”.
    • “Sentences that contain nominalizations are dealt with using a small hand-crafted resource (lexicon of nominalizations) 3 which helps us to cope with the most important cases, e.g. “to edit 􀀀a text ” 􀀀 “editor of 􀀀a text ”/“􀀀text editor”. The system also includes hyponomy and synonymy relations based on the WordNet model.

2006

2003

  • (Ding et al., 2003)
  • 2003_EventInfoExtractionUsingLinkGrammar.
    • The rules express what type of words must be to the left and to the right of the word.
    • Where possible, we try to give link-types names that have mnemonic significance in this way.
    • “Each word in the dictionary is associated with a set of links. A link ending with ‘+’ implies that word has to make that link with some word to its right and similarly ‘-’ stands for a link with a word to its left. A typical entry in the dictionary is man : D- & (O- or S+)"
  • H. 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). pp 16-22. (notes)(paper)

2002

1998

1995

1993

  • D. D. Sleator and D. Temperley. (1993). Parsing English with a Link Grammar. Third International Workshop on Parsing Technologies. (notes) (paper)
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