Link Grammar Improvements


The last version of the parser, version 3.0, was released in August 1998. The new version, 4.0, reflects some important changes. As well as some modest improvements in vocabulary and coverage, there are these significant new features:

  1. The new version has what we call a "phrase-parser": a system which takes a "linkage" (the usual link grammar representation of a sentence, showing links connecting pairs of words) and derives a constituent or phrase-structure representation, showing conventional phrase categories such as noun phrase (NP), verb phrase (VP), prepositional phrase(PP), clause (S), and so on. Click here for more information about this. You can also experiment with this feature using the online version of the parser (click here).

  2. Another new feature of version 4.0 is "morpho-guessing" of unknown words. While earlier versions were able to guess the part of speech of a word based on its context, the new version also considers its spelling. For example, words ending in "-ed" are assumed to be past-tense verbs; words ending in "-ing" are assumed to be present participles. This greatly improves the ability of the parser to handle sentences containing multiple unknown words. Click here for more information about this.

  3. The new system features an improved system for handling punctuation. As in the previous version, punctuation symbols are "stripped off" of words, in that a space is inserted between the symbol and a neighboring word. In the new version, however, the symbols to be stripped off in this way can easily be specified and modified by the user, using an "affix file" which is read in by the parser when the program is run. This may also be useful for other phenomena besides punctuation, particularly for those designing parsers for other languages. Click here for more information about this.

  4. The new release includes a small system for English-to-German translation; it also includes a small German dictionary which can be used for parsing German sentences. Click here for more information about this.