/*
 * The Apache Software License, Version 1.1
 *
 *
 * Copyright (c) 1999 The Apache Software Foundation.  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.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:  
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Xalan" and "Apache Software Foundation" must
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 * 5. Products derived from this software may not be called "Apache",
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 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
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 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation and was
 * originally based on software copyright (c) 1999, Lotus
 * Development Corporation., http://www.lotus.com.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */
package org.apache.xpath;

import javax.xml.transform.SourceLocator;

/**
 * A class that implements this interface can construct expressions, 
 * give information about child and parent expressions,
 * and give the originating source information.  A class that implements 
 * this interface does not lay any claim to being directly executable.
 * 
 * <p>Note: This interface should not be considered stable.  Only exprSetParent 
 * and exprGetParent can be counted on to work reliably.  Work in progress.</p>
 */
public interface ExpressionNode extends SourceLocator
{
  /** This pair of methods are used to inform the node of its
    parent. */
  public void exprSetParent(ExpressionNode n);
  public ExpressionNode exprGetParent();

  /** This method tells the node to add its argument to the node's
    list of children.  */
  public void exprAddChild(ExpressionNode n, int i);

  /** This method returns a child node.  The children are numbered
     from zero, left to right. */
  public ExpressionNode exprGetChild(int i);

  /** Return the number of children the node has. */
  public int exprGetNumChildren();
}