An Abstract Machine for Typed Feature Structures

This paper describes an abstract machine for linguistic formalisms that are based on typed feature structures, such as HPSG. The core design of the abstract machine is given in detail, including the compilation process from a high-level language to the abstract machine language and the implementation of the abstract instructions. The machine's engine supports the unification of typed, possibly cyclic, feature structures. A separate module deals with control structures and instructions to accommodate parsing for phrase structure grammars. We treat the linguistic formalism as a high-level declarative programming language, applying methods that were proved useful in computer science to the study of natural languages: a grammar specified using the formalism is endowed with an operational semantics.