/**
* Copyright (c) 2009/09-2012/08, Regents of the University of Colorado
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
* ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/**
* Copyright 2012/09-2013/04, 2013/11-Present, University of Massachusetts Amherst
* Copyright 2013/05-2013/10, IPSoft Inc.
*
* 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 com.clearnlp.conversion;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import com.clearnlp.constituent.CTLib;
import com.clearnlp.constituent.CTNode;
import com.clearnlp.constituent.CTTree;
import com.clearnlp.dependency.DEPNode;
import com.clearnlp.dependency.DEPTree;
import com.clearnlp.headrule.HeadRule;
import com.clearnlp.headrule.HeadRuleMap;
import com.clearnlp.headrule.HeadTagSet;
import com.clearnlp.pattern.PTPunct;
import com.clearnlp.reader.AbstractColumnReader;
/**
* Abstract constituent to dependency converter.
* @since 1.0.0
* @author Jinho D. Choi ({@code jdchoi77@gmail.com})
*/
abstract public class AbstractC2DConverter
{
protected HeadRuleMap m_headrules;
public AbstractC2DConverter(HeadRuleMap headrules)
{
m_headrules = headrules;
}
/**
* Sets the head of the specific node and all its sub-nodes.
* Calls {@link AbstractC2DConverter#findHeads(CTNode)}.
* @param curr the node to process.
*/
protected void setHeads(CTNode curr)
{
// terminal nodes become the heads of themselves
if (!curr.isPhrase())
{
curr.c2d = new C2DInfo(curr);
return;
}
// set the heads of all children
for (CTNode child : curr.getChildren())
setHeads(child);
// stop traversing if it is the top node
if (curr.isPTag(CTLib.PTAG_TOP))
return;
// only one child
if (curr.getChildrenSize() == 1)
{
curr.c2d = new C2DInfo(curr.getChild(0));
return;
}
// find the headrule of the current node
HeadRule rule = m_headrules.get(curr.pTag);
if (rule == null)
{
System.err.println("Error: headrules not found for \""+curr.pTag+"\"");
rule = m_headrules.get(CTLib.PTAG_X);
}
setHeadsAux(rule, curr);
}
/**
* Returns the head of the specific node list according to the specific headrule.
* Every other node in the list becomes the dependent of the head node.
* @param rule the headrule to be consulted.
* @param nodes the list of nodes.
* @param flagSize the number of head flags.
* @return the head of the specific node list according to the specific headrule.
*/
protected CTNode getHead(HeadRule rule, List<CTNode> nodes, int flagSize)
{
nodes = new ArrayList<CTNode>(nodes);
if (rule.isRightToLeft()) Collections.reverse(nodes);
int i, size = nodes.size(), flag;
int[] flags = new int[size];
for (i=0; i<size; i++)
flags[i] = getHeadFlag(nodes.get(i));
CTNode head = null, child;
outer: for (flag=0; flag<flagSize; flag++)
{
for (HeadTagSet tagset : rule.getHeadTags())
{
for (i=0; i<size; i++)
{
child = nodes.get(i);
if (flags[i] == flag && tagset.matches(child))
{
head = child;
break outer;
}
}
}
}
if (head == null)
{
System.err.println("Error: head not found.");
System.exit(1);
}
CTNode parent = head.getParent();
for (CTNode node : nodes)
{
if (node != head && !node.c2d.hasHead())
node.c2d.setHead(head, getDEPLabel(node, parent, head));
}
return head;
}
/** @return the dependency tree converted from the specific constituent tree without head information. */
protected DEPTree initDEPTree(CTTree cTree)
{
DEPTree dTree = new DEPTree();
String form, lemma, pos;
DEPNode dNode;
int id;
for (CTNode node : cTree.getTokens())
{
id = node.getTokenId() + 1;
form = PTPunct.revertBracket(node.form);
lemma = AbstractColumnReader.BLANK_COLUMN;
pos = node.pTag;
dNode = new DEPNode(id, form, lemma, pos, node.c2d.d_feats);
dTree.add(dNode);
}
dTree.initXHeads();
return dTree;
}
/**
* Sets the head of the specific phrase node.
* This is a helper method of {@link AbstractC2DConverter#setHeads(CTNode)}.
* @param rule the headrule to the specific node.
* @param curr the phrase node.
*/
abstract protected void setHeadsAux(HeadRule rule, CTNode curr);
/**
* Returns the head flag of the specific constituent node.
* @param child the constituent node.
* @return the head flag of the specific constituent node.
*/
abstract protected int getHeadFlag(CTNode child);
/**
* Returns a dependency label given the specific phrase structure.
* @param C the current node.
* @param P the parent of {@code C}.
* @param p the head of {@code P}.
* @return a dependency label given the specific phrase structure.
*/
abstract protected String getDEPLabel(CTNode C, CTNode P, CTNode p);
/**
* Returns the dependency tree converted from the specific constituent tree.
* If the constituent tree contains only empty categories, returns {@code null}.
* @param cTree the constituent tree to convert.
* @return the dependency tree converted from the specific constituent tree.
*/
abstract public DEPTree toDEPTree(CTTree cTree);
}