Fluid construction grammar
Encyclopedia
Fluid construction grammar (FCG) is a construction grammar
formalism designed by Luc Steels
implementing the notion of emergent grammar
and operates from a multi-agent perspective (none of the agents will speak exactly the same language
), useful for studies in evolutionary linguistics
.
FCG is a fully operational formalism for construction grammars and proposes a uniform mechanism for parsing
and production. It integrates many notions from contemporary computational linguistics
such as feature structure
and unification-based language processing. Rules are considered bi-directional and hence usable both for parsing and production. Processing is flexible in the sense that it can even cope with 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 conducted at Sony
CSL in Paris and the AI
Lab at the Vrije Universiteit Brussel
.
objects that are coupled during a parsing or production operation. One feature structure, designated the 'Left Pole', contains the semantic units. Each named unit is a set of features and their values. The other feature structure, the 'Right Pole', contains the syntactic units. Words are represented by units. Groupings of sub-units into grammatical constructions are also represented by units. The 'subunits' feature links subordinate units into a tree rooted at the 'top' unit. The majority of units in the FCG Left Pole have corresponding same-named units in the Right Pole, thus forming similar unit trees.
During the FCG parse of an utterance, the initial state of the Coupled Feature Structure is for a set of word strings and their ordering to be present on the sole unit of the Right (syntactic) Pole named 'top', and for the Left (semantic) Pole to consist of an empty top unit. As production rules apply consecutively to the Coupled Feature Structure, units and lexical features are linked into the Right Pole tree for each word, and if the word is significant, same-named units with semantic features are added to the Left Pole tree. At the end of a successful parse, the meaning (logical form (linguistics)
) is extracted from the 'meaning' features of Left Pole units.
Conversely, because the FCG grammar is bi-directional, the production of an utterance from an initial set of meanings begins with the meanings as feature values of the sole Left Pole unit named 'top'. As successive grammar rules are applied, same-named units are added to both pole trees. At the end of a successful production, the word string is extracted from the 'form' features of Right Pole units.
. With rule variables bound, the rule pole not used in the match is merged with the corresponding pole of the Coupled Feature Structure. One type of rule, the Construction Rule, is an exception and is allowed to merge both Left and Right Poles with the Coupled Feature Structure after the matching process binds its free variables.
Construction grammar
The term construction grammar covers a family of theories, or models, of grammar that are based on the idea that the primary unit of grammar is the grammatical construction rather than the atomic syntactic unit and the rule that combines atomic units, and that the grammar of a language is made up...
formalism designed by Luc Steels
Luc Steels
Luc Steels is a Belgian scientist, and Director of the Artificial Intelligence Laboratory of the Vrije Universiteit Brussel. He is also heading the Sony Computer Science Laboratory in Paris. Steels, along with Rodney Brooks , was one of the initiators of the behaviour-based robotics approach to...
implementing the notion of emergent grammar
Emergent grammar
Emergent grammar is an approach to the study of syntax, originally proposed by Paul Hopper, which postulates that rules for grammar and syntactic structure emerge as language is used...
and operates from a multi-agent perspective (none of the agents will speak exactly the same language
Language
Language may refer either to the specifically human capacity for acquiring and using complex systems of communication, or to a specific instance of such a system of complex communication...
), useful for studies in evolutionary linguistics
Evolutionary linguistics
Evolutionary linguistics is the scientific study of the origins and development of language. The main challenge in this research is the lack of empirical data: spoken language leaves practically no traces. This led to an abandonment of the field for more than a century...
.
FCG is a fully operational formalism for construction grammars and proposes a uniform mechanism for parsing
Parsing
In computer science and linguistics, parsing, or, more formally, syntactic analysis, is the process of analyzing a text, made of a sequence of tokens , to determine its grammatical structure with respect to a given formal grammar...
and production. It integrates many notions from contemporary computational linguistics
Computational linguistics
Computational linguistics is an interdisciplinary field dealing with the statistical or rule-based modeling of natural language from a computational perspective....
such as feature structure
Feature structure
In phrase structure grammars, such as generalised phrase structure grammar, head-driven phrase structure grammar and lexical functional grammar, a feature structure is essentially a set of attribute-value pairs. For example the attribute named number might have the value singular. The value of an...
and unification-based language processing. Rules are considered bi-directional and hence usable both for parsing and production. Processing is flexible in the sense that it can even cope with 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 conducted at Sony
Sony
, commonly referred to as Sony, is a Japanese multinational conglomerate corporation headquartered in Minato, Tokyo, Japan and the world's fifth largest media conglomerate measured by revenues....
CSL in Paris and the AI
Ai
AI, A.I., Ai, or ai may refer to:- Computers :* Artificial intelligence, a branch of computer science* Ad impression, in online advertising* .ai, the ISO Internet 2-letter country code for Anguilla...
Lab at the Vrije Universiteit Brussel
Vrije Universiteit Brussel
The Vrije Universiteit Brussel is a Flemish university located in Brussels, Belgium. It has two campuses referred to as Etterbeek and Jette.The university's name is sometimes abbreviated by "VUB" or translated to "Free University of Brussels"...
.
Coupled feature structure
FCG provides two transient feature structureFeature structure
In phrase structure grammars, such as generalised phrase structure grammar, head-driven phrase structure grammar and lexical functional grammar, a feature structure is essentially a set of attribute-value pairs. For example the attribute named number might have the value singular. The value of an...
objects that are coupled during a parsing or production operation. One feature structure, designated the 'Left Pole', contains the semantic units. Each named unit is a set of features and their values. The other feature structure, the 'Right Pole', contains the syntactic units. Words are represented by units. Groupings of sub-units into grammatical constructions are also represented by units. The 'subunits' feature links subordinate units into a tree rooted at the 'top' unit. The majority of units in the FCG Left Pole have corresponding same-named units in the Right Pole, thus forming similar unit trees.
During the FCG parse of an utterance, the initial state of the Coupled Feature Structure is for a set of word strings and their ordering to be present on the sole unit of the Right (syntactic) Pole named 'top', and for the Left (semantic) Pole to consist of an empty top unit. As production rules apply consecutively to the Coupled Feature Structure, units and lexical features are linked into the Right Pole tree for each word, and if the word is significant, same-named units with semantic features are added to the Left Pole tree. At the end of a successful parse, the meaning (logical form (linguistics)
Logical form (linguistics)
In the field of linguistics, particularly in the minimalist program, Logical Form , refers to a mental representation of a linguistic expression, derived solely from Surface Structure. In the words of Chomsky, LF captures "those aspects of semantic representation that are strictly determined by...
) is extracted from the 'meaning' features of Left Pole units.
Conversely, because the FCG grammar is bi-directional, the production of an utterance from an initial set of meanings begins with the meanings as feature values of the sole Left Pole unit named 'top'. As successive grammar rules are applied, same-named units are added to both pole trees. At the end of a successful production, the word string is extracted from the 'form' features of Right Pole units.
Grammar production rules
FCG rules are a persistent specialization of Coupled Feature Structures, having the additional attributes of type, name, and weight. FCG applies rules by type, and distinguishes among them by name. Weights can be used to choose between competing rules. Some types of FCG rule match the rule Left Pole with the corresponding Coupled Feature Structure Left Pole. The remaining types of FCG rule match Right Poles with the Coupled Feature Structure. A match generally follows the process of unificationUnification
Unification, in computer science and logic, is an algorithmic process by which one attempts to solve the satisfiability problem. The goal of unification is to find a substitution which demonstrates that two seemingly different terms are in fact either identical or just equal...
. With rule variables bound, the rule pole not used in the match is merged with the corresponding pole of the Coupled Feature Structure. One type of rule, the Construction Rule, is an exception and is allowed to merge both Left and Right Poles with the Coupled Feature Structure after the matching process binds its free variables.
Flexibility
FCG provides a framework for bi-directional parsing and production. But aside from reserving the 'top' unit name and a few feature names, FCG makes no commitments to any grammatical theory of word categories, and makes no commitment to any particular theory of grammatical constructions. Users of FCG make these choices by writing FGC grammar rules accordingly.External links
- http://www.fcg-net.org/ (website of the FCG community)
- http://www.emergent-languages.org/
- Texai open source Java FCG implementation