Fluid construction grammar
Fluid construction grammar is an open-source computational construction grammar formalism that allows computational linguists to formally write down the inventory of lexical and grammatical constructions as well as to do experiments in language learning and language evolution. FCG is an open instrument that can be used by construction grammarians who want to formulate their intuitions and data in a precise way and who want to test the implications of their grammar designs for language parsing, production and learning. The formalism can be tested through an interactive web interface at .
FCG integrates many notions from contemporary computational linguistics such as feature structure and unification-based language processing, but uses them in a novel way to operationalize insights from construction grammar theory. Constructions are considered bi-directional and hence usable both for parsing and production. Processing is flexible in the sense that FCG provides meta-layer processing for coping with novelty, partially ungrammatical or incomplete sentences. FCG is called 'fluid' because it acknowledges the premise that language users constantly change and update their grammars. The research on FCG is primarily carried out by Luc Steels and his teams at the in Brussels and the in Barcelona, and the in Paris. Besides Steels, current and former contributors to the FCG formalism include,,, Joris Bleys, Joachim De Beule, Martin Loetzsch, Nicolas Neubauer, Michael Spranger, Wouter Van den Broeck, Pieter Wellens, and others.
Transient structure
FCG treats parsing and production as a search problem, in which the FCG engine searches for the best utterance to verbalize a meaning or the best semantic network to analyze an utterance. Each state representation in the search process is called a Transient Structure. A Transient Structure can be considered as an extended feature structure, as it consists of a list of "units" that consist of a unit-name and a unit-body. Older versions of FCG used to split the transient structure into two separate poles for semantics and syntax, but the current version implements a single representation for all linguistic information.Constructions
FCG constructions are treated as the operators of the search process. That is, by applying a construction to a transient structure, a new transient structure in the search space may be created. Just like transient structures, constructions mostly consists of units of feature-value pairs. Constructions are however more structured because they contain two distinct parts:- A conditional part: This part of the construction specifies the conditions under which the construction may apply. Moreover, units of features that appear in the conditional part are split into a "comprehension lock" and a "formulation lock". This split is important for ensuring the bidirectional application of an FCG construction.
- A Contributing part: This part of the construction specifies information that the construction may add to the transient structure if the conditions for application are satisfied.