Björn Bringert

PGF: A Portable Run-time Format for Type-theoretical Grammars

Portable Grammar Format (PGF) is a core language for type-theoretical grammars. It is the target language to which grammars written in the high-level formalism Grammatical Framework (GF) are compiled. Low-level and simple, PGF is easy to reason about, so that its language-theoretic properties can be established. It is also easy to write interpreters that perform parsing and generation with PGF grammars, and compilers converting PGF to other formats. This paper gives a concise description of PGF, covering syntax, semantics, and parser generation. It also discusses the technique of embedded grammars, where language processing tasks defined by PGF grammars are integrated in larger systems.

Speech Recognition Grammar Compilation in Grammatical Framework

This paper describes how grammar-based language models for speech recognition systems can be generated from Grammatical Framework (GF) grammars. Context-free grammars and finite-state models can be generated in several formats: GSL, SRGS, JSGF, and HTK SLF. In addition, semantic interpretation code can be embedded in the generated context-free grammars. This enables rapid development of portable, multilingual and easily modifiable speech recognition applications.

A pattern for almost compositional functions

This paper introduces a pattern for almost compositional functions over recursive data types, and over families of mutually recursive data types. Here almost compositional means that for a number of the constructors in the type(s), the result of the function depends only on the constructor and the results of calling the function on the constructors arguments. The pattern consists of a generic part constructed once for each data type or family of data types, and a task-specific part. The generic part contains the code for the predictable compositional cases, leaving the interesting work to the task-specific part. Examples of the pattern implemented in dependent type theory with inductive families, in Haskell with generalized algebraic data types and rank-2 polymorphism, and in Java using a variant of the Visitor design pattern are given. The relationship to the Scrap Your Boilerplate approach to generic programming, and to general tree types in dependent type theory are also investigated.

Student paper: HaskellDB improved

We present an improved version of the HaskellDB database library. The original version relied on TRex, a Haskell extension supported only by the Hugs interpreter. We have replaced the use of TRex by a record implementation which uses more commonly implemented Haskell extensions.Additionally, HaskellDB now supports two different cross-platform database backends. Other changes include database creation functionality, bounded string support, performance enhancements, fixes to the optimisation logic, transaction support and more fine grained expression types.

Grammatical Framework Web Service

We present a web service for natural language parsing, prediction, generation, and translation using grammars in Portable Grammar Format (PGF), the target format of the Grammatical Framework (GF) grammar compiler. The web service implementation is open source, works with any PGF grammar, and with any web server that supports FastCGI. The service exposes a simple interface which makes it possible to use it for interactive natural language web applications. We describe the functionality and interface of the web service, and demonstrate several applications built on top of it.

Interactive Multilingual Web Applications with Grammatical Framework

We present an approach to multilingual web content based on multilingual grammars and syntax editing for a controlled language. Content can be edited in any supported language and it is automatically kept within a controlled language fragment. We have implemented a web-based syntax editor for Grammatical Framework (GF) grammars which allows both direct abstract syntax tree manipulation and text input in any of the languages supported by the grammar. With this syntax editor and the GF JavaScript API, GF grammars can be used to build multilingual web applications. As a demonstration, we have implemented an example application in which users can add, edit and review restaurants in English, Spanish and Swedish.

Grammar Development in GF

GF is a grammar formalism that has a powerful type system and module system, permitting a high level of abstraction and division of labour in grammar writing. GF is suited both for expert linguists, who appreciate its capacity of generalizations and conciseness, and for beginners, who benefit from its static type checker and, in particular, the GF Resource Grammar Library, which currently covers 12 languages. GF has a notion of multilingual grammars, enabling code sharing, linguistic generalizations, rapid development of translation systems, and painless porting of applications to new languages.