1 research outputs found
Parsing with Traces: An Algorithm and a Structural Representation
General treebank analyses are graph structured, but parsers are typically
restricted to tree structures for efficiency and modeling reasons. We propose a
new representation and algorithm for a class of graph structures that is
flexible enough to cover almost all treebank structures, while still admitting
efficient learning and inference. In particular, we consider directed, acyclic,
one-endpoint-crossing graph structures, which cover most long-distance
dislocation, shared argumentation, and similar tree-violating linguistic
phenomena. We describe how to convert phrase structure parses, including
traces, to our new representation in a reversible manner. Our dynamic program
uniquely decomposes structures, is sound and complete, and covers 97.3% of the
Penn English Treebank. We also implement a proof-of-concept parser that
recovers a range of null elements and trace types.Comment: To appear in Transactions of the Association for Computational
Linguistic