---
title: "Factored A* Search for Models over Sequences and Trees"
authors:
  - "Dan Klein"
  - "Christopher D. Manning"
doi: ""
url: "https://ijcai.org/proceedings/2003/177"
pdf: "https://ijcai.org/proceedings/2003/0177.pdf"
venue: "Proceedings of the Eighteenth International Joint Conference on Artificial Intelligence"
year: 2003
pages: "1246-1250"
track: ""
keywords:
---

# Factored A* Search for Models over Sequences and Trees

Dan Klein, Christopher D. Manning

*Proceedings of the Eighteenth International Joint Conference on Artificial Intelligence*, pages 1246-1250.

## Abstract

We investigate the calculation of A* bounds for sequence and tree models which are the explicit intersection of a set of simpler models or can be bounded by such an intersection. We provide a natural viewpoint which unifies various instances of factored A* models for trees and sequences, some previously known and others novel, including multiple sequence alignment, weighted finitestate transducer composition, and lexicalized statistical parsing. The specific case of parsing with a product of syntactic (PCFG) and semantic (lexical dependency) components is then considered in detail. We show that this factorization gives a modular lexicalized parser which is simpler than comparably accurate non-factored models, and which allows efficient exact inference with large treebank grammars.