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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.dependency.DependencyTreeNode;

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 MinimumMiniparTemplateAcceptor
 * @see MaximumMiniparTemplateAcceptor
 */
public class MediumMiniparTemplateAcceptor implements DependencyPathAcceptor {

    static final Set MEDIUM_TEMPLATES = new HashSet();

    static {
        MEDIUM_TEMPLATES.add("A:mod:N,N:lex-mod:(null)");
        MEDIUM_TEMPLATES.add("A:mod:N,N:nn:N");
        MEDIUM_TEMPLATES.add("A:subj:N,N:lex-mod:(null)");
        MEDIUM_TEMPLATES.add("A:subj:N,N:nn:N");
        MEDIUM_TEMPLATES.add("N:conj:N,N:lex-mod:(null)");
        MEDIUM_TEMPLATES.add("N:conj:N,N:nn:N");
        MEDIUM_TEMPLATES.add("N:gen:N,N:lex-mod:(null)");
        MEDIUM_TEMPLATES.add("N:gen:N,N:nn:N");
        MEDIUM_TEMPLATES.add("N:nn:N,N:conj:N");
        MEDIUM_TEMPLATES.add("N:nn:N,N:conj:N,N:nn:N");
        MEDIUM_TEMPLATES.add("N:nn:N,N:gen:N");
        MEDIUM_TEMPLATES.add("N:nn:N,N:gen:N,N:nn:N");
        MEDIUM_TEMPLATES.add("N:nn:N,N:mod:A");
        MEDIUM_TEMPLATES.add("N:nn:N,N:mod:Pred");
        MEDIUM_TEMPLATES.add("N:nn:N,N:obj:V");
        MEDIUM_TEMPLATES.add("N:nn:N,N:subj:A");
        MEDIUM_TEMPLATES.add("N:nn:N,N:subj:V");
        MEDIUM_TEMPLATES.add("(null):lex-mod:N,N:conj:N");
        MEDIUM_TEMPLATES.add("(null):lex-mod:N,N:conj:N,N:lex-mod:(null)");
        MEDIUM_TEMPLATES.add("(null):lex-mod:N,N:gen:N");
        MEDIUM_TEMPLATES.add("(null):lex-mod:N,N:gen:N,N:lex-mod:(null)");
        MEDIUM_TEMPLATES.add("(null):lex-mod:N,N:mod:A");
        MEDIUM_TEMPLATES.add("(null):lex-mod:N,N:mod:Pred");
        MEDIUM_TEMPLATES.add("(null):lex-mod:N,N:obj:V");
        MEDIUM_TEMPLATES.add("(null):lex-mod:N,N:subj:A");
        MEDIUM_TEMPLATES.add("(null):lex-mod:N,N:subj:V");
        MEDIUM_TEMPLATES.add("Prep:mod:N,N:lex-mod:(null)");
        MEDIUM_TEMPLATES.add("Prep:mod:N,N:nn:N");
        MEDIUM_TEMPLATES.add("V:obj:N,N:lex-mod:(null)");
        MEDIUM_TEMPLATES.add("V:obj:N,N:nn:N");
        MEDIUM_TEMPLATES.add("V:subj:N,N:lex-mod:(null)");
        MEDIUM_TEMPLATES.add("V:subj:N,N:nn:N");
    }
    
    /**
     * Creates the acceptor with its standard templates
     */
    public MediumMiniparTemplateAcceptor() { }
   
    /**
     * 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) {
        // First check whether the minimum template acceptor would allow this
        // path
        if (MinimumMiniparTemplateAcceptor.acceptsInternal(path))
            return true;

        // Filter out paths that can't match the template due to length
        if (path.length() > 3)
            return false;

        int pathLength = path.length();

        // The medium set of templates contains "null" matches which are wild
        // cards against any part of speech.  We handle these by generating
        // three possible patterns that could represent the provided path.  If
        // any of these patterns are found in the medium set, the path is valid.
        StringBuilder nullStart = new StringBuilder(pathLength * 16);
        StringBuilder nullEnd = new StringBuilder(pathLength * 16);
        StringBuilder noNulls = new StringBuilder(pathLength * 16);

        // Iterate over each pair in the path and create the pattern string that
        // represents this path.  The pattern string is pos:rel:pos[,...] .
        DependencyTreeNode first = path.first();
        for (int i = 1; i < pathLength; ++i) {
            DependencyTreeNode second = path.getNode(i);
            // 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 (first.word().equals(IteratorFactory.EMPTY_TOKEN))
                return false;

            // Get the relation between the two nodes
            String rel = path.getRelation(i - 1);
            String firstPos = first.pos();
            String secPos = second.pos();
            
            nullStart.append((i == 0) ? "(null)" : firstPos);
            nullStart.append(":").append(rel).append(":").append(secPos);

            nullEnd.append(firstPos).append(":").append(rel).append(":");
            nullEnd.append((i + 1 == pathLength) ? "(null)" : secPos);

            noNulls.append(firstPos).append(":").append(rel)
                .append(":").append(secPos);

            // Check whether more elements existing, and if so, add the ','
            if (i + 1 < pathLength) {
                nullStart.append(",");
                nullEnd.append(",");
                noNulls.append(",");
            }

            // Last, shift over the node
            first = second;
        }
        
        // Extra case for the last token in the path
        if (first.word().equals(IteratorFactory.EMPTY_TOKEN))
            return false;

        return MEDIUM_TEMPLATES.contains(noNulls.toString())
            || MEDIUM_TEMPLATES.contains(nullStart.toString())
            || MEDIUM_TEMPLATES.contains(nullEnd.toString());
    }

    /**
     * {@inheritDoc}
     */
    public int maxPathLength() {
        return 4;
    }
}