Synchronous and Multicomponent Tree-Adjoining Grammars: Complexity, Algorithms and Linguistic Applications

This thesis addresses the design of appropriate formalisms and algorithms to be used for natural language processing. This entails a delicate balance between the ability of a formalism to capture the linguistic generalizations required by natural language processing applications and the ability of a natural language processing application based on the formalism to process the formalism efficiently enough to be useful. I focus on the Tree-Adjoining Grammar formalism as a base and on the mechanism of grammar synchronization for managing relationships between the input and output of a natural language processing system. Grammar synchronization is a formal concept by which the derivations of two distinct grammars occur in tandem so that a single isomorphic derivation produces distinct derived structures in each of the synchronized grammars. Using synchronization implies a strong assumption—one that I seek to justify in the second part of the thesis—namely that certain critical relationships in natural language applications, such as the relationship between the syntax and semantics of a language or the relationship between the syntax of two natural languages, are close enough to be expressed with grammars that share a derivational structure. The extent of the isomorphism between the derived structures of the related lan-