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Grammatical Framework (GF) is a programming language for writing grammars of natural languages. GF is capable of parsing and generating texts in several languages simultaneously while working from a language-independent representation of meaning. Grammars written in GF can be compiled into a platform independent format and then used from different programming languages including C and Java, C#, Python and Haskell. A companion to GF is the GF Resource Grammar Library, a reusable library for dealing with the morphology and syntax of a growing number of natural languages.
Both GF itself and the GF Resource Grammar Library are open-source. Typologically, GF is a functional programming language. Mathematically, it is a type-theoretic formal system (a logical framework to be precise) based on Martin-Löf's intuitionistic type theory, with additional judgments tailored specifically to the domain of linguistics.
Goal: write a multilingual grammar for expressing statements about John and Mary loving each other. [2]
In GF, grammars are divided to two module types:
cat
and fun
. cat
or category declarations list categories i.e. all the possible types of trees there can be.fun
or function declarations state functions and their types, these must be implemented by concrete modules (see below).lincat
and lin
. lincat
or linearization type definitions, says what type of objects linearization produces for each category listed in cat
.lin
or linearization rules implement functions declared in fun
. They say how trees are linearized.Consider the following:
Abstract syntax
abstractZero={catS;NP;VP;V2;funPred:NP->VP->S;Compl:V2->NP->VP;John,Mary:NP;Love:V2;}
Concrete syntax: English
concreteZeroEngofZero={lincatS,NP,VP,V2=Str;linPrednpvp=np++vp;Complv2np=v2++np;John="John";Mary="Mary";Love="loves";}
Notice: Str
(token list or "string") as the only linearization type.
A single abstract syntax may be applied to many concrete syntaxes, in our case one for each new natural language we wish to add. The same system of trees can be given:
Concrete syntax: French
concreteZeroFreofZero={lincatS,NP,VP,V2=Str;linPrednpvp=np++vp;Complv2np=v2++np;John="Jean";Mary="Marie";Love="aime";}
We can now use our grammar to translate phrases between French and English. The following commands can be executed in the GF interactive shell.
Import many grammars with the same abstract syntax
> import ZeroEng.gf ZeroFre.gf Languages: ZeroEng ZeroFre
Translation: pipe linearization to parsing
> parse -lang=Eng "John loves Mary"| linearize -lang=Fre Jean aime Marie
Multilingual generation: linearize into all languages
> generate_random | linearize -treebank Zero: Pred Mary (Compl Love Mary)ZeroEng: Mary loves MaryZeroFre: Marie aime Marie
Latin has cases: nominative for subject, accusative for object.
We use a parameter type for case (just 2 of Latin's 6 cases). The linearization type of NP is a table type: from Case
to Str
. The linearization of John
is an inflection table. When using an NP, we select (!
) the appropriate case from the table.
Concrete syntax: Latin
concreteZeroLatofZero={lincatS,VP,V2=Str;NP=Case=>Str;linPrednpvp=np!Nom++vp;Complv2np=np!Acc++v2;John=table{Nom=>"Ioannes";Acc=>"Ioannem"};Mary=table{Nom=>"Maria";Acc=>"Mariam"};Love="amat";paramCase=Nom|Acc;}
In Dutch, the verb heeft lief is a discontinuous constituent. The linearization type of V2
is a record type with two fields. The linearization of Love
is a record. The values of fields are picked by projection (.
)
Concrete syntax: Dutch
concreteZeroDutofZero={lincatS,NP,VP=Str;V2={v:Str;p:Str};linPrednpvp=np++vp;Complv2np=v2.v++np++v2.p;John="Jan";Mary="Marie";Love={v="heeft";p="lief"};}
For Hebrew, NP has gender as its inherent feature – a field in the record. VP has gender as its variable feature – an argument of a table. In predication, the VP receives the gender of the NP.
Concrete syntax: Hebrew
concreteZeroHebofZero={flagscoding=utf8;lincatS=Str;NP={s:Str;g:Gender};VP,V2=Gender=>Str;linPrednpvp=np.s++vp!np.g;Complv2np=table{g=>v2!g++"את"++np.s};John={s="ג׳ון";g=Masc};Mary={s="מרי";g=Fem};Love=table{Masc=>"אוהב";Fem=>"אוהבת"};paramGender=Masc|Fem;}
GF has inbuilt functions which can be used for visualizing parse trees and word alignments.
The following commands will generate parse trees for the given phrases and open the produced PNG image using the system's eog
command.
> parse -lang=Eng "John loves Mary"| visualize_parse -view="eog"> parse -lang=Dut "Jan heeft Marie lief"| visualize_parse -view="eog"
![]() | ![]() |
In general, this gives phrase alignment. Links can be crossing, phrases can be discontinuous. The align_words
command follows a similar syntax:
> parse -lang=Fre "Marie aime Jean"| align_words -lang=Fre,Dut,Lat -view="eog"
In natural language applications, libraries are a way to cope with thousands of details involved in syntax, lexicon, and inflection. The GF Resource Grammar Library is the standard library for Grammatical Framework. It covers the morphology and basic syntax for an increasing number of languages, currently including Afrikaans, Amharic (partial), Arabic (partial), Basque (partial), Bulgarian, Catalan, Chinese, Czech (partial), Danish, Dutch, English, Estonian, Finnish, French, German, Greek ancient (partial), Greek modern, Hebrew (fragments), Hindi, Hungarian (partial), Interlingua, Italian, Japanese, Korean (partial), Latin (partial), Latvian, Maltese, Mongolian, Nepali, Norwegian bokmål, Norwegian nynorsk, Persian, Polish, Punjabi, Romanian, Russian, Sindhi, Slovak (partial), Slovene (partial), Somali (partial), Spanish, Swahili (fragments), Swedish, Thai, Turkish (fragments), and Urdu. In addition, 14 languages have WordNet lexicon and large-scale parsing extensions. [3]
A full API documentation of the library can be found at the RGL Synopsis page. The RGL status document gives the languages currently available in the GF Resource Grammar Library, including their maturity.
GF was first created in 1998 at Xerox Research Centre Europe, Grenoble, in the project Multilingual Document Authoring. At Xerox, it was used for prototypes including a restaurant phrase book, a database query system, a formalization of an alarm system instructions with translations to 5 languages, and an authoring system for medical drug descriptions.
Later projects using GF and involving third parties include:
Academically, GF has been used in many PhD theses and resulted in a lot of scientific publications (see the GF publication list for some of them).
Commercially, GF has been used by a number of companies, in domains such as e-commerce, health care and translating formal specifications to natural language. [4]
There is an active group for developers and users of GF alike, located at https://groups.google.com/group/gf-dev
The seventh GF summer school, postponed due to COVID-19, is to be held in Singapore. Co-organised with the Singapore Management University's Centre for Computational Law, the summer school will have a special focus on computational law.
The sixth GF summer school was the first one held outside Europe. The major themes of the summer school were African language resources, and the growing usage of GF in commercial applications.
The fifth GF summer school was held in Riga, Latvia. This summer school had a number of participant from startups, presenting industrial use cases of GF.
GF was one of the four platforms featured at the Summer School in Rule-Based Machine Translation, along with Apertium, Matxin and TectoMT.
The fourth GF summer school was held on Gozo island in Malta. Like the previous edition in 2013, this summer school featured collaborations with other resources, such as Apertium and FrameNet.
The third GF Summer school, was held on Frauenchiemsee island in Bavaria, Germany with the special theme "Scaling up Grammar Resources". This summer school focused on extending the existing resource grammars with the ultimate goal of dealing with any text in the supported languages. Lexicon extension is an obvious part of this work, but also new grammatical constructions were also of interest. There was a special interest in porting resources from other open-source approaches, such as WordNets and Apertium, and reciprocally making GF resources easily reusable in other approaches.
The second GF Summer school, subtitled Frontiers of Multilingual Technologies was held in 2011 in Barcelona, Spain. It was sponsored by CLT, the Centre for Language Technology of the University of Gothenburg, and by UPC, Universitat Politècnica de Catalunya. The School addressed new languages and also promoted ongoing work in those languages which are already under construction. Missing EU languages were especially encouraged.
The school began with a 2-day GF tutorial, serving those interested in getting an introduction to GF or an overview of on-going work.
All results of the summer school are available as open-source software released under the LGPL license.
The first GF summer school was held in 2009 in Gothenburg, Sweden. It was a collaborative effort to create grammars of new languages in Grammatical Framework, GF. These grammars were added to the Resource Grammar Library, which previously had 12 languages. Around 10 new languages are already under construction, and the School aimed to address 23 new languages. All results of the Summer School were made available as open-source software released under the LGPL license.
The summer school was organized by the Language Technology Group at the Department of Computer Science and Engineering. The group is a part of the Centre of Language Technology, a focus research area of the University of Gothenburg.
The code created by the school participants is made accessible in the GF darcs repository, subdirectory contrib/summerschool.
In linguistics, syntax is the study of how words and morphemes combine to form larger units such as phrases and sentences. Central concerns of syntax include word order, grammatical relations, hierarchical sentence structure (constituency), agreement, the nature of crosslinguistic variation, and the relationship between form and meaning (semantics). There are numerous approaches to syntax that differ in their central assumptions and goals.
In grammar, a phrase—called expression in some contexts—is a group of words or singular word acting as a grammatical unit. For instance, the English expression "the very happy squirrel" is a noun phrase which contains the adjective phrase "very happy". Phrases can consist of a single word or a complete sentence. In theoretical linguistics, phrases are often analyzed as units of syntactic structure such as a constituent.
In computer science, the Cocke–Younger–Kasami algorithm is a parsing algorithm for context-free grammars published by Itiroo Sakai in 1961. The algorithm is named after some of its rediscoverers: John Cocke, Daniel Younger, Tadao Kasami, and Jacob T. Schwartz. It employs bottom-up parsing and dynamic programming.
A parse tree or parsing tree or derivation tree or concrete syntax tree is an ordered, rooted tree that represents the syntactic structure of a string according to some context-free grammar. The term parse tree itself is used primarily in computational linguistics; in theoretical syntax, the term syntax tree is more common.
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Lexical functional grammar (LFG) is a constraint-based grammar framework in theoretical linguistics. It posits two separate levels of syntactic structure, a phrase structure grammar representation of word order and constituency, and a representation of grammatical functions such as subject and object, similar to dependency grammar. The development of the theory was initiated by Joan Bresnan and Ronald Kaplan in the 1970s, in reaction to the theory of transformational grammar which was current in the late 1970s. It mainly focuses on syntax, including its relation with morphology and semantics. There has been little LFG work on phonology.
Parsing, syntax analysis, or syntactic analysis is the process of analyzing a string of symbols, either in natural language, computer languages or data structures, conforming to the rules of a formal grammar. The term parsing comes from Latin pars (orationis), meaning part.
Dependency grammar (DG) is a class of modern grammatical theories that are all based on the dependency relation and that can be traced back primarily to the work of Lucien Tesnière. Dependency is the notion that linguistic units, e.g. words, are connected to each other by directed links. The (finite) verb is taken to be the structural center of clause structure. All other syntactic units (words) are either directly or indirectly connected to the verb in terms of the directed links, which are called dependencies. Dependency grammar differs from phrase structure grammar in that while it can identify phrases it tends to overlook phrasal nodes. A dependency structure is determined by the relation between a word and its dependents. Dependency structures are flatter than phrase structures in part because they lack a finite verb phrase constituent, and they are thus well suited for the analysis of languages with free word order, such as Czech or Warlpiri.
The term phrase structure grammar was originally introduced by Noam Chomsky as the term for grammar studied previously by Emil Post and Axel Thue. Some authors, however, reserve the term for more restricted grammars in the Chomsky hierarchy: context-sensitive grammars or context-free grammars. In a broader sense, phrase structure grammars are also known as constituency grammars. The defining trait of phrase structure grammars is thus their adherence to the constituency relation, as opposed to the dependency relation of dependency grammars.
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Rule-based machine translation is machine translation systems based on linguistic information about source and target languages basically retrieved from dictionaries and grammars covering the main semantic, morphological, and syntactic regularities of each language respectively. Having input sentences, an RBMT system generates them to output sentences on the basis of morphological, syntactic, and semantic analysis of both the source and the target languages involved in a concrete translation task.
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