With the emergence of Grammar Engineering as a discipline within Natural Language Processing, there is a clear need for a deeper understanding of the processes of grammar development and the tools and techniques required to support these processes.
The formalisms with which grammatical theories are expressed, and subsequently with which particular grammars are implemented, are core components of the grammar development process. While the majority of formalisms in common use have settled on a number of key technologies, such as (typed) feature structures and unification, a common approax:h to the treatment of free word order has not yet been reached.
We take a systematic approach to evaluating the different approaches to free word order within the major syntactic representational styles, namely dependency structure, phrase structure, and hybrid structures (which incorporate both dependency and phrase structure) in order to determine which, if any, holds a particular advantage for representing free word order languages from the perspective of the grammar developer. We closely examine the intrinsic properties of each formalism in order to identify the reasons for any particular advantage or disadvantage.
In the course of this investigation, we developed a framework for usability evaluation of grammar formalisms based on IS09126 quality characteristics and existing quality requirements for grammar formalisms. We also developed a set of metrics for measuring conformance with these requirements. As a result of the investigation, we present a number of recommendations for improving grammar formalisms for the representation of free word order phenomena.