Grammatical Framework

Version 3.1
December 2009

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What is GF

GF, Grammatical Framework, is a programming language for multilingual grammar applications. It is

• a special-purpose language for grammars, like YACC, Bison, Happy, BNFC, but not restricted to programming languages
• a functional language, like Haskell, Lisp, OCaml, Scheme, SML, but specialized to grammar writing
• a natural language processing framework, like LKB, XLE, Regulus, but based on functional programming and type theory
• a categorial grammar formalism, like ACG, CCG, but different and equipped with different tools
• a logical framework, like Agda, Coq, Isabelle, but equipped with concrete syntax in addition to logic

Don't worry if you don't know most of the references above - but if you do know at least one, it may help you to get a first idea of what GF is.

Applications

GF can be used for building

• text translators
• multilingual web gadgets
• speech translators
• natural-language interfaces
• multilingual authoring systems
• dialogue systems
• natural language resources

Availability

GF is open-source, licensed under GPL (the program) and LGPL (the libraries). It is available for

• Linux
• Mac OS X
• Windows
• via compilation to JavaScript, almost any platform that has a web browser

Projects

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, in chronological order,

• GF-Alfa: natural language interface to formal proofs
• Efficient: authoring tool for business models.
• GF-KeY: authoring and translation of software specifications
• TALK: multilingual and multimodal spoken dialogue systems
• WebALT: multilingual generation of mathematical exercises (commercial project)
• SALDO: Swedish morphological dictionary based on rules developed for GF and Functional Morphology

Academically, GF has been used in four PhD theses and resulted in around fifty scientific publications (see GF publication list).

Programming in GF

GF is easy to learn by following the tutorial. You can write your first translator in 15 minutes.

GF has an interactive command interpreter, as well as a batch compiler. Grammars can be compiled to parser and translator code in many different formats. These components can then be embedded in applications written in other programming languages. The formats currently supported are:

• Haskell
• JavaScript
• Speech recognition: HTK/ATK, Nuance, JSGF

The GF programming language is high-level and advanced, featuring

• static type checking
• higher-order functions
• dependent types
• pattern matching with data constructors and regular expressions
• module system with multiple inheritance and parametrized modules

Libraries

Libraries are at the heart of modern software engineering. 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 has support for an increasing number of languages, currently including

1. Arabic (partial)
2. Bulgarian
3. Catalan
4. Danish
5. Dutch
6. English
7. Finnish
8. French
9. German
10. Hindi/Urdu (fragments)
11. Interlingua
12. Italian
13. Latin (fragments)
14. Norwegian bokmål
15. Polish
16. Romanian
17. Russian
18. Spanish
19. Swedish
20. Thai (fragments)

Adding a language to the resource library takes 3 to 9 months - contributions are welcome! You can start with the resource grammarian's tutorial.