Abstract

Parsing natural language is an attempt to discover some structure in a text (or textual representation) generated by a person. This structure can be put to a variety of uses, including machine translation, grammar conformance checking, and determination of prosody in text-to-speech tasks. Recent theories of Syntax use Unification to better describe the intricacies of natural language [137]. For parsing systems, unification techniques have been either added to a context-free base system [152, 40, 4, 23], or replaced the context-free base entirely [118, 135, 45] (possibly putting it back later [136]). The seemingly small step of adding unification has opened a Pandora’s Box of computational complexity, increasing the difficulty of the problem from polynomial [48] to somewhere between NP-complete and intractable, depending on the details of the unification system and how it was added [10]. Worse, unification on a context-free base parser can break the packing technique used to address the problem of ambiguity, leading to exponential blow-ups of the parser’s performance in both space and time in practice. I propose

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