  This paper describes a first step towards the definition of 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 specification language to
the abstract machine language and the implementation of the abstract
instructions. We thus apply 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. Currently, our machine supports the
unification of simple feature structures, unification of sequences of such
structures, cyclic structures and disjunction.
