Fully Lexicalized Head-Driven Syntactic Generation
Tilman Becker · 1998
We describe a new approach to syntactic generation with Head-Driven Phrase Structure Grammars (HPSG) that uses an extensive off--line preprocessing step. Direct generation algorithms apply the phrase-structure rules (schemata) of the grammar on--line which is an computationally expensive step. Instead, we collect off-line for every lexical type of the HPSG grammar all minimally complete projections (called elementary trees) that can be derived with the schemata. This process is known as `compiling HPSG to TAG' and derives a Lexicalized Tree-Adjoining Grammar (LTAG). The representation as an LTAG is `fully lexicalized' in the sense that all grammatical information is directly encoded with the lexical item (as a set of elementary trees) and the combination operations are reduced from schema applications to the TAG primitives of adjunction and substitution. Given this LTAG, the generation task has a very different search space that can be traversed very efficiently, avoiding the...