The Mechanics of the Grammatical Framework

Abstract: Grammatical Framework (GF) is a well known theoretical framework and a mature programming language for the description of natural languages. The GF community is growing rapidly and the range of applications is expanding. Within the framework, there are computational resources for 26 languages created from different people in different organizations. The coverage of the different resources varies but there are complete morphologies and grammars for at least 20 languages. This advancement would not be possible without the continuous development of the GF compiler and interpreter. The demand for efficient and portable execution model for GF has led to major changes in both the compiler and the interpreter. We developed a new low-level representation called Portable Grammar Format (PGF) which is simple enough for an efficient interpretation. Since it was already known that a major fragment of GF is equivalent to Parallel Multiple Context-Free Grammar (PMCFG), we designed PGF as an extension that adds to PMCFG distinctive features of GF such as multilingualism, higher-order abstract syntax, dependent types, etc. In the process we developed novel algorithms for parsing and linearization with PMCFG and a framework for logical reasoning in first-order type theory where the proof search can be constrained by the parse chart. This monograph is the detailed description of the engine for efficient interpretation of PGF and is intended as a reference for building alternative implementations and as a foundation for the future development of PGF.