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.Collection;
import java.util.LinkedList;
import org.junit.BeforeClass;
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 static Collection<String> terminals;
  private static Collection<String> nonTerminals; // PoS + Parse tags
  private static String startSymbol;
  private static Collection<Rule> rules;

  @BeforeClass
  public static void setUp() throws Exception {
    nonTerminals = new LinkedList<String>();
    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");

    startSymbol = "S";

    terminals = new LinkedList<String>();
    terminals.add("works");
    terminals.add("saw");
    terminals.add("man");
    terminals.add("woman");
    terminals.add("car");
    terminals.add("the");
    terminals.add("with");
    terminals.add("in");
    terminals.add("joe");
    terminals.add("john");
    terminals.add("sam");
    terminals.add("michael");
    terminals.add("michelle");
    terminals.add("scarlett");
    terminals.add("and");
    terminals.add("but");
    terminals.add("while");
    terminals.add("of");
    terminals.add("for");

    rules = new LinkedList<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", "works"));
    rules.add(new Rule("Vt", "saw"));
    rules.add(new Rule("NN", "man"));
    rules.add(new Rule("NN", "woman"));
    rules.add(new Rule("NN", "car"));
    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", "joe"));
    rules.add(new Rule("NNP", "john"));
    rules.add(new Rule("NNP", "sam"));
    rules.add(new Rule("NNP", "michael"));
    rules.add(new Rule("NNP", "michelle"));
    rules.add(new Rule("NNP", "scarlett"));
    rules.add(new Rule("CJ", "and"));
    rules.add(new Rule("DJ", "but"));
    rules.add(new Rule("DJ", "while"));
  }

  @Test
  public void testSingleSentenceExpansion() throws Exception {
    ContextFreeGrammar contextFreeGrammar = new ContextFreeGrammar(nonTerminals, terminals, rules, startSymbol);
    String[] expansion = contextFreeGrammar.leftMostDerivation("S");
    checkExpansion(expansion);
  }

  @Test
  public void testSingleSentenceRandomExpansion() throws Exception {
    ContextFreeGrammar contextFreeGrammar = new ContextFreeGrammar(nonTerminals, terminals, rules, startSymbol, true);
    String[] expansion = contextFreeGrammar.leftMostDerivation("S");
    checkExpansion(expansion);
  }


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

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

  @Test
  public void testMultipleSentencesRandomExpansion() throws Exception {
    ContextFreeGrammar contextFreeGrammar = new ContextFreeGrammar(nonTerminals, terminals, rules, startSymbol, true);
    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));
    }
  }
}