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The S-Space Package is a collection of algorithms for building Semantic Spaces as well as a highly-scalable library for designing new distributional semantics algorithms. Distributional algorithms process text corpora and represent the semantic for words as high dimensional feature vectors. This package also includes matrices, vectors, and numerous clustering algorithms. These approaches are known by many names, such as word spaces, semantic spaces, or distributed semantics and rest upon the Distributional Hypothesis: words that appear in similar contexts have similar meanings.

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/*
 * Copyright 2010 David Jurgens 
 *
 * This file is part of the S-Space package and is covered under the terms and
 * conditions therein.
 *
 * The S-Space package is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as published
 * by the Free Software Foundation and distributed hereunder to you.
 *
 * THIS SOFTWARE IS PROVIDED "AS IS" AND NO REPRESENTATIONS OR WARRANTIES,
 * EXPRESS OR IMPLIED ARE MADE.  BY WAY OF EXAMPLE, BUT NOT LIMITATION, WE MAKE
 * NO REPRESENTATIONS OR WARRANTIES OF MERCHANT- ABILITY OR FITNESS FOR ANY
 * PARTICULAR PURPOSE OR THAT THE USE OF THE LICENSED SOFTWARE OR DOCUMENTATION
 * WILL NOT INFRINGE ANY THIRD PARTY PATENTS, COPYRIGHTS, TRADEMARKS OR OTHER
 * RIGHTS.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program. If not, see .
 */

package edu.ucla.sspace.dv;

import edu.ucla.sspace.dependency.DependencyPath;
import edu.ucla.sspace.dependency.DependencyPathAcceptor;

import edu.ucla.sspace.text.IteratorFactory;

import java.util.HashSet;
import java.util.Set;


/**      
 * A {@code DependencyPathAcceptor} that accepts the minimum set of path
 * templates specified by Padó and
 * Lapata (2007).  This acceptor is designed to be used with the Minipar parser
 * and its associated part of speech tag set
 *
 * @see MediumMiniparTemplateAcceptor
 * @see MaximumMiniparTemplateAcceptor
 */
public class MinimumMiniparTemplateAcceptor implements DependencyPathAcceptor {

    static final Set MINIMUM_TEMPLATES = new HashSet();

    static {
        MINIMUM_TEMPLATES.add(toPattern("A", "amod", "V"));
        MINIMUM_TEMPLATES.add(toPattern("A", "amod", "A"));
        MINIMUM_TEMPLATES.add(toPattern("A", "mod", "A"));
        MINIMUM_TEMPLATES.add(toPattern("A", "mod", "N"));
        MINIMUM_TEMPLATES.add(toPattern("A", "mod", "Prep"));
        MINIMUM_TEMPLATES.add(toPattern("A", "mod", "V"));
        MINIMUM_TEMPLATES.add(toPattern("A", "subj", "N"));
        MINIMUM_TEMPLATES.add(toPattern("N", "conj", "N"));
        MINIMUM_TEMPLATES.add(toPattern("N", "gen", "N"));
        MINIMUM_TEMPLATES.add(toPattern("N", "mod", "A"));
        MINIMUM_TEMPLATES.add(toPattern("N", "mod", "Prep"));
        MINIMUM_TEMPLATES.add(toPattern("N", "nn", "N"));
        MINIMUM_TEMPLATES.add(toPattern("N", "obj", "V"));
        MINIMUM_TEMPLATES.add(toPattern("N", "pcomp-n", "Prep"));
        MINIMUM_TEMPLATES.add(toPattern("N", "subj", "A"));
        MINIMUM_TEMPLATES.add(toPattern("N", "subj", "N"));
        MINIMUM_TEMPLATES.add(toPattern("N", "subj", "V"));
        MINIMUM_TEMPLATES.add(toPattern(null, "lex-mod", "V"));
        MINIMUM_TEMPLATES.add(toPattern("Prep", "mod", "A"));
        MINIMUM_TEMPLATES.add(toPattern("Prep", "mod", "N"));
        MINIMUM_TEMPLATES.add(toPattern("Prep", "mod", "V"));   
        MINIMUM_TEMPLATES.add(toPattern("Prep", "pcomp-n", "N"));
        MINIMUM_TEMPLATES.add(toPattern("V", "amod", "A"));
        MINIMUM_TEMPLATES.add(toPattern("V", "lex-mod", null));
        MINIMUM_TEMPLATES.add(toPattern("V", "mod", "A"));
        MINIMUM_TEMPLATES.add(toPattern("V", "mod", "Prep"));
        MINIMUM_TEMPLATES.add(toPattern("V", "obj", "N"));
        MINIMUM_TEMPLATES.add(toPattern("V", "subj", "N"));
    };
    
    /**
     * Creates the acceptor with its standard templates
     */
    public MinimumMiniparTemplateAcceptor() { }
   
    /**
     * Returns {@code true} if the path matches one of the predefined templates
     *
     * @param path a dependency path
     *
     * @return {@code true} if the path matches a template
     */
    public boolean accepts(DependencyPath path) {
        return acceptsInternal(path);
    }
    
    /**
     * A package-private method that checks whether the path matches any of the
     * predefined templates.  This method is provided so other template classes
     * have access to the accept logic used by this class.
     *
     * @param path a dependency path
     *
     * @return {@code true} if the path matches a template
     */
    static boolean acceptsInternal(DependencyPath path) {
        // Filter out paths that can't match the template due to length
        if (path.length() != 2)
            return false;
        
        // Check that the nodes weren't filtered out.  If so reject the path
        // even if the part of speech and relation text may have matched a
        // template.
        if (path.getNode(0).word().equals(IteratorFactory.EMPTY_TOKEN)
                || path.getNode(0).word().equals(IteratorFactory.EMPTY_TOKEN))
            return false;

        String pos1 = path.getNode(0).pos();
        String rel = path.getRelation(0);
        String pos2 = path.getNode(1).pos();

        return MINIMUM_TEMPLATES.contains(toPattern(pos1, rel, pos2));
    }

    /**
     * {@inheritDoc}
     */
    public int maxPathLength() {
        return 2;
    }
    
    /**
     * Returns the pattern string for the provided parts of speech and relation.
     */
    static String toPattern(String pos1, String rel, String pos2) {
        return pos1 + ":" + rel + ":" + pos2;
    }

}