Abstract
Head-driven phrase structure grammar
(HPSG) enjoys a uniform formalism representing rich contextual syntactic and even
semantic meanings. This paper makes the
first attempt to formulate a simplified HPSG
by integrating constituent and dependency
formal representations into head-driven phrase
structure. Then two parsing algorithms are
respectively proposed for two converted tree
representations, division span and joint span.
As HPSG encodes both constituent and dependency structure information, the proposed
HPSG parsers may be regarded as a sort of
joint decoder for both types of structures and
thus are evaluated in terms of extracted or
converted constituent and dependency parsing
trees. Our parser achieves new state-of-the-art
performance for both parsing tasks on Penn
Treebank (PTB) and Chinese Penn Treebank,
verifying the effectiveness of joint learning
constituent and dependency structures. In
details, we report 95.84 F1 of constituent
parsing and 97.00% UAS of dependency
parsing on PTB.