Amalia -- Abstract MAchine for LInguistic Applications

Thursday, 19 Feburary 1998, 4:00pm
Shuly Wintner
Tuebingen

Contemporary linguistic formalisms such as LFG or HPSG have become so rigorous that it is now possible to view them as very high level declarative programming languages. Consequently, grammars for natural languages can be viewed as programs; this view enables the application of various methods and techniques that were proved useful for programming languages to the domain of natural languages. This work introduces such an application: an implementation technique that is common for logic programming languages, namely the use of an abstract machine, is applied to (a subset of) the ALE formalism, originally designed for specifying feature-structure based phrase-structure grammars.

We present Amalia (Abstract MAchine for LInguistic Applications), an abstract machine specifically tailored for processing ALE grammars. It is composed of data structures and a set of instructions, augmented by a compiler from the grammatical formalism to the abstract instructions, and a (portable) interpreter of the abstract instructions. The effect of each instruction is defined using a low-level language that can be executed on ordinary hardware. Execution of the compiled code amounts to parsing with respect to the original grammar. A variant of the compiler produces code for generation.

The advantages of the abstract machine approach are twofold. From a theoretical point of view, the abstract machine gives a well-defined operational semantics to the grammatical formalism. From a practical point of view, Amalia is the first system that employs a direct compilation scheme for unification grammars that are based on typed feature structures. The use of Amalia results in a much improved performance over existing systems.