Web1TWriter.java

/*
 * Copyright 2011
 * Ubiquitous Knowledge Processing (UKP) Lab
 * Technische Universität Darmstadt
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package de.tudarmstadt.ukp.dkpro.core.io.web1t;

import java.io.IOException;
import java.util.Set;

import org.apache.uima.UimaContext;
import org.apache.uima.analysis_engine.AnalysisEngineProcessException;
import org.apache.uima.fit.component.JCasAnnotator_ImplBase;
import org.apache.uima.fit.descriptor.ConfigurationParameter;
import org.apache.uima.fit.descriptor.MimeTypeCapability;
import org.apache.uima.fit.descriptor.TypeCapability;
import org.apache.uima.jcas.JCas;
import org.apache.uima.resource.ResourceInitializationException;

import de.tudarmstadt.ukp.dkpro.core.api.parameter.ComponentParameters;
import de.tudarmstadt.ukp.dkpro.core.api.parameter.MimeTypes;
import de.tudarmstadt.ukp.dkpro.core.io.web1t.util.Web1TConverter;

/**
 * Web1T n-gram index format writer.
 */
@MimeTypeCapability({MimeTypes.TEXT_X_NGRAM})
@TypeCapability(
        inputs={
            "de.tudarmstadt.ukp.dkpro.core.api.segmentation.type.Sentence"})
public class Web1TWriter
	extends JCasAnnotator_ImplBase
{
	/**
	 * Types to generate n-grams from.
	 *
	 * Example: {@code Token.class.getName() + "/pos/PosValue"} for part-of-speech n-grams
	 */
	public static final String PARAM_INPUT_TYPES = "inputTypes";
	@ConfigurationParameter(name = PARAM_INPUT_TYPES, mandatory = true)
	private Set<String> inputPaths;

	/**
	 * Location to which the output is written.
	 */
	public static final String PARAM_TARGET_LOCATION = ComponentParameters.PARAM_TARGET_LOCATION;
	@ConfigurationParameter(name = PARAM_TARGET_LOCATION, mandatory = true)
	private String outputPath;

	/**
	 * Character encoding of the output data.
	 */
	public static final String PARAM_TARGET_ENCODING = ComponentParameters.PARAM_TARGET_ENCODING;
	@ConfigurationParameter(name = PARAM_TARGET_ENCODING, mandatory = false, defaultValue = "UTF-8")
	private String outputEncoding;

	/**
	 * Minimum n-gram length.
	 *
	 * Default: {@code 1}
	 */
	public static final String PARAM_MIN_NGRAM_LENGTH = "minNgramLength";
	@ConfigurationParameter(name = PARAM_MIN_NGRAM_LENGTH, mandatory = false, defaultValue = "1")
	private int minNgramLength;

	/**
	 * Maximum n-gram length.
	 *
	 * Default: {@code 3}
	 */
	public static final String PARAM_MAX_NGRAM_LENGTH = "maxNgramLength";
	@ConfigurationParameter(name = PARAM_MAX_NGRAM_LENGTH, mandatory = false, defaultValue = "3")
	private int maxNgramLength;

	/**
	 * Create a lower case index.
	 */
	public static final String PARAM_LOWERCASE = "lowercase";
	@ConfigurationParameter(name = PARAM_LOWERCASE, mandatory = false, defaultValue = "false")
	private boolean lowercase;

	/**
	 * Create the indexes that jWeb1T needs to operate. (default: true)
	 */
	public static final String PARAM_CREATE_INDEXES = "createIndexes";
	@ConfigurationParameter(name = PARAM_CREATE_INDEXES, mandatory = false, defaultValue = "true")
	private boolean createIndexes;

	/**
	 * Specifies the minimum frequency a NGram must have to be written to the
	 * final index. The specified value is interpreted as inclusive value, the
	 * default is 1. Thus, all NGrams with a frequency of at least 1 or higher
	 * will be written.
	 */
	public static final String PARAM_MIN_FREQUENCY = "minFreq";
	@ConfigurationParameter(name = PARAM_MIN_FREQUENCY, mandatory = false, defaultValue = "1")
	private int minFreq;

	/**
	 * The input file(s) is/are split into smaller files for quick access. An
	 * own file is created if the first two starting letters (or the starting
	 * letter if the word has a length of 1 character) account for at least x%
	 * of all starting letters in the input file(s). The default value for
	 * splitting a file is 1.0%. Every word that has starting characters which
	 * does not suffice the threshold is written with other words that also did
	 * not meet the threshold into an own file for miscellaneous words. A high
	 * threshold will lead to only a few, but large files and a most likely very
	 * large misc. file. A low threshold results in many small files. Use a zero or a negative
	 * value to write everything to one file.
	 */
	public static final String PARAM_SPLIT_TRESHOLD = "splitFileTreshold";
	@ConfigurationParameter(name = PARAM_SPLIT_TRESHOLD, mandatory = false, defaultValue = "1.0")
	private float splitThreshold;

	/**
	 * The type being used for segments
	 */
    public static final String PARAM_CONTEXT_TYPE = "contextType";
    @ConfigurationParameter(name = PARAM_CONTEXT_TYPE, mandatory = true, defaultValue="de.tudarmstadt.ukp.dkpro.core.api.segmentation.type.Sentence")
    protected String contextType;


	private Web1TConverter converter;

	@Override
	public void initialize(UimaContext context)
		throws ResourceInitializationException
	{
		super.initialize(context);

		try {
            this.converter = new Web1TConverter(outputPath, minNgramLength, maxNgramLength);
        }
        catch (IOException e) {
            throw new ResourceInitializationException(e);
        }

		converter.setWriteIndexes(createIndexes);
		converter.setSplitThreshold(splitThreshold);
		converter.setMinFrequency(minFreq);
		converter.setToLowercase(lowercase);
		converter.setOutputEncoding(outputEncoding);
	}

    @Override
    public void process(JCas jcas)
        throws AnalysisEngineProcessException
    {

        try {
            converter.add(jcas, inputPaths, jcas.getCas().getTypeSystem().getType(contextType));
        }
        catch (IOException e) {
            throw new AnalysisEngineProcessException(e);
        }
    }

    /**
	 * The input files for each ngram level is read, splitted according to the
	 * frequency of the words starting letter in the files and the split files
	 * are individually sorted and consolidated.
	 */
	@Override
	public void collectionProcessComplete()
		throws AnalysisEngineProcessException
	{
		super.collectionProcessComplete();

		try {
            converter.createIndex();
        }
        catch (IOException e) {
            throw new AnalysisEngineProcessException(e);
        }
	}
}