link grammar

The Link Grammar Parser exhibits the linguistic (natural language) structure of English, Thai, Russian, Arabic, Persian and limited subsets of a half-dozen other languages. This structure is a graph of typed links (edges) between the words in a sentence. One may obtain the more conventional HPSG (constituent) and dependency style parses from Link Grammar by applying a collection of rules to convert to these different formats. This is possible because Link Grammar goes a bit "deeper" into the "syntactico-semantic" structure of a sentence: it provides considerably more fine-grained and detailed information than what is commonly available in conventional parsers. The theory of Link Grammar parsing was originally developed in 1991 by Davy Temperley, John Lafferty and Daniel Sleator, at the time professors of linguistics and computer science at the Carnegie Mellon University. The three initial publications on this theory provide the best introduction and overview; since then, there have been hundreds of publications further exploring, examining and extending the ideas. Although based on the original Carnegie-Mellon code base, the current Link Grammar package has dramatically evolved and is profoundly different from earlier versions. There have been innumerable bug fixes; performance has improved by several orders of magnitude. The package is fully multi-threaded, fully UTF-8 enabled, and has been scrubbed for security, enabling cloud deployment. Parse coverage of English has been dramatically improved; other languages have been added (most notably, Thai and Russian). There is a raft of new features, including support for morphology, dialects, and a fine-grained weight (cost) system, allowing vector-embedding-like behaviour. There is a new, sophisticated tokenizer tailored for morphology: it can offer alternative splittings for morphologically ambiguous words. Dictionaries can be updated at run-time, enabling systems that perform continuous learning of grammar to also parse at the same time. That is, dictionary updates and parsing are mutually thread-safe. Classes of words can be recognized with regexes. Random planar graph parsing is fully supported; this allows uniform sampling of the space of planar graphs. A detailed report of what has changed can be found in the ChangeLog. Please see the main web page for more information. This version is a continuation of the original CMU parser. New! As of version 5.9.0, the system include an experimental system for generating sentences. These are specified using a "fill in the blanks" API, where words are substituted into wild-card locations, whenever the result is a grammatically valid sentence. Additional details are in the man page: man link-generator (in the man subdirectory). This generator is used in the OpenCog Language Learning project, which aims to automatically learn Link Grammars from corpora, using brand-new and innovative information theoretic techniques, somewhat similar to those found in artificial neural nets (deep learning), but using explicitly symbolic representations. The parser includes API's in various different programming languages, as well as a handy command-line tool for playing with it. Here's some typical output: This rather busy display illustrates many interesting things. For example, the Ss b link connects the verb and the subject, and indicates that the subject is singular. Likewise, the Ost link connects the verb and the object, and also indicates that the object is singular. The WV (verb-wall) link points at the head-verb of the sentence, while the Wd link points at the head-noun. The Xp link connects to the trailing punctuation. The Ds c link connects the noun to the determiner: it again confirms that the noun is singular, and also that the noun starts with a consonant. (The PH link, not required here, is used to force phonetic agreement, distinguishing 'a' from 'an'). These link types are documented in the English Link Documentation. The bottom of