nlp-utils/src/test/java/org/apache/opennlp/utils/cfg/ContextFreeGrammarTest.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.opennlp.utils.cfg;

import java.util.Arrays;
import java.util.HashSet;
import java.util.Set;
import org.junit.Before;
import org.junit.Test;

import static org.junit.Assert.assertNotNull;
import static org.junit.Assert.assertTrue;

/**
 * Testcase for {@link org.apache.opennlp.utils.cfg.ContextFreeGrammar}
 */
public class ContextFreeGrammarTest {

  private ContextFreeGrammar contextFreeGrammar;
  private Set<String> terminals;

  @Before
  public void setUp() throws Exception {

    Set<String> nonTerminals = new HashSet<String>(); // PoS + Parse tags
    nonTerminals.add("S");
    nonTerminals.add("NP");
    nonTerminals.add("VP");
    nonTerminals.add("PP");
    nonTerminals.add("DT");
    nonTerminals.add("Vi");
    nonTerminals.add("Vt");
    nonTerminals.add("NN");
    nonTerminals.add("IN");
    nonTerminals.add("NNP");
    nonTerminals.add("CJ");
    nonTerminals.add("DJ");
    nonTerminals.add("P");

    String startSymbol = "S";

    terminals = new HashSet<String>();
    terminals.add("sleeps");
    terminals.add("saw");
    terminals.add("man");
    terminals.add("woman");
    terminals.add("telescope");
    terminals.add("the");
    terminals.add("with");
    terminals.add("in");
    terminals.add("tommaso");
    terminals.add("simone");
    terminals.add("joao");
    terminals.add("tigro");
    terminals.add("michele");
    terminals.add("scarlett");
    terminals.add("and");
    terminals.add("but");
    terminals.add("while");
    terminals.add("of");
    terminals.add("for");

    Set<Rule> rules = new HashSet<Rule>();
    rules.add(new Rule("S", "NP", "VP"));
    rules.add(new Rule("P", "S", "CJ", "S"));
    rules.add(new Rule("P", "S", "DJ", "S"));
    rules.add(new Rule("VP", "Vi"));
    rules.add(new Rule("VP", "Vt", "NP"));
    rules.add(new Rule("VP", "VP", "PP"));
    rules.add(new Rule("NP", "DT", "NN"));
    rules.add(new Rule("NP", "NP", "PP"));
    rules.add(new Rule("NP", "NNP"));
    rules.add(new Rule("PP", "IN", "NP"));
    rules.add(new Rule("Vi", "sleeps"));
    rules.add(new Rule("Vt", "saw"));
    rules.add(new Rule("NN", "man"));
    rules.add(new Rule("NN", "woman"));
    rules.add(new Rule("NN", "telescope"));
    rules.add(new Rule("DT", "the"));
    rules.add(new Rule("IN", "with"));
    rules.add(new Rule("IN", "in"));
    rules.add(new Rule("IN", "for"));
    rules.add(new Rule("IN", "of"));
    rules.add(new Rule("NNP", "tommaso"));
    rules.add(new Rule("NNP", "simone"));
    rules.add(new Rule("NNP", "joao"));
    rules.add(new Rule("NNP", "tigro"));
    rules.add(new Rule("NNP", "michele"));
    rules.add(new Rule("NNP", "scarlett"));
    rules.add(new Rule("CJ", "and"));
    rules.add(new Rule("DJ", "but"));
    rules.add(new Rule("DJ", "while"));

    contextFreeGrammar = new ContextFreeGrammar(nonTerminals, terminals, rules, startSymbol);
  }

  @Test
  public void testSingleExpansion() throws Exception {
    String[] expansion = contextFreeGrammar.leftMostDerivation("S");
    checkExpansion(expansion);
  }


  @Test
  public void testMultipleSentencesExpansion() throws Exception {
    String[] expansion = contextFreeGrammar.leftMostDerivation("S", "CJ", "S");
    checkExpansion(expansion);

    expansion = contextFreeGrammar.leftMostDerivation("S", "DJ", "S", "CJ", "P");
    checkExpansion(expansion);
  }

  private void checkExpansion(String[] expansion) {
    assertNotNull(expansion);
    assertTrue(expansion.length > 0);
    for (String t : expansion) {
      assertTrue("term " + t + " is not a terminal symbol", terminals.contains(t));
    }
    System.err.println(Arrays.toString(expansion));
  }
}