opennlp.tools.chunker
Class DefaultChunkerContextGenerator

java.lang.Object
  opennlp.tools.chunker.DefaultChunkerContextGenerator

All Implemented Interfaces:

ChunkerContextGenerator, BeamSearchContextGenerator<String>

public class DefaultChunkerContextGenerator
extends Object
implements ChunkerContextGenerator

Features based on chunking model described in Fei Sha and Fernando Pereira. Shallow parsing with conditional random fields. In Proceedings of HLT-NAACL 2003. Association for Computational Linguistics, 2003.

Author:

Tom Morton

Constructor Summary

DefaultChunkerContextGenerator()
Creates the default context generator a chunker.

Method Summary

String[]	getContext(int index, String[] sequence, String[] priorDecisions, Object[] additionalContext) Returns the context for the specified position in the specified sequence (list).
String[]	getContext(int i, String[] toks, String[] tags, String[] preds) Returns the contexts for chunking of the specified index.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

DefaultChunkerContextGenerator

public DefaultChunkerContextGenerator()

Creates the default context generator a chunker.

Method Detail

getContext

public String[] getContext(int index,
                           String[] sequence,
                           String[] priorDecisions,
                           Object[] additionalContext)

Description copied from interface: BeamSearchContextGenerator

Returns the context for the specified position in the specified sequence (list).

Specified by:

getContext in interface BeamSearchContextGenerator<String>

Parameters:

index - The index of the sequence.

sequence - The sequence of items over which the beam search is performed.

priorDecisions - The sequence of decisions made prior to the context for which this decision is being made.

additionalContext - Any addition context specific to a class implementing this interface.

Returns:

the context for the specified position in the specified sequence.

getContext

public String[] getContext(int i,
                           String[] toks,
                           String[] tags,
                           String[] preds)

Description copied from interface: ChunkerContextGenerator

Returns the contexts for chunking of the specified index.

Specified by:

getContext in interface ChunkerContextGenerator

Parameters:

i - The index of the token in the specified toks array for which the context should be constructed.

toks - The tokens of the sentence. The toString methods of these objects should return the token text.

tags - The POS tags for the the specified tokens.

preds - The previous decisions made in the taging of this sequence. Only indices less than i will be examined.

Returns:

An array of predictive contexts on which a model basis its decisions.