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

PGF (Portable Grammar Format) is a low-level language used as a target of compiling grammars written in GF (Grammatical Framework). 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 format. 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.