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MXP1 is a stable XmlPull parsing engine that is based on ideas from XPP and in particular XPP2 but completely revised and rewritten to take the best advantage of latest JIT JVMs such as Hotspot in JDK 1.4+.
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/*
 * $Header: /l/extreme/cvs/codes/XPP3/java/src/java/xpath/org/xmlpull/v1/builder/xpath/jaxen/VariableContext.java,v 1.1 2004/06/16 15:55:34 aslom Exp $
 * $Revision: 1.1 $
 * $Date: 2004/06/16 15:55:34 $
 *
 * ====================================================================
 *
 * Copyright (C) 2000-2002 bob mcwhirter & James Strachan.
 * 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 disclaimer that follows 
 *    these conditions in the documentation and/or other materials 
 *    provided with the distribution.
 *
 * 3. The name "Jaxen" must not be used to endorse or promote products
 *    derived from this software without prior written permission.  For
 *    written permission, please contact [email protected].
 * 
 * 4. Products derived from this software may not be called "Jaxen", nor
 *    may "Jaxen" appear in their name, without prior written permission
 *    from the Jaxen Project Management ([email protected]).
 * 
 * In addition, we request (but do not require) that you include in the 
 * end-user documentation provided with the redistribution and/or in the 
 * software itself an acknowledgement equivalent to the following:
 *     "This product includes software developed by the
 *      Jaxen Project (http://www.jaxen.org/)."
 * Alternatively, the acknowledgment may be graphical using the logos 
 * available at http://www.jaxen.org/
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED 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 Jaxen AUTHORS OR THE PROJECT
 * 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.
 *
 * ====================================================================
 * This software consists of voluntary contributions made by many 
 * individuals on behalf of the Jaxen Project and was originally 
 * created by bob mcwhirter  and 
 * James Strachan .  For more information on the 
 * Jaxen Project, please see .
 * 
 * $Id: VariableContext.java,v 1.1 2004/06/16 15:55:34 aslom Exp $
 */


package org.xmlpull.v1.builder.xpath.jaxen;

/** Resolves variable bindings within an XPath expression.
 *
 *  
 *  Variables within an XPath expression are denoted using
 *  notation such as $varName or $nsPrefix:varName, and may
 *  refer to primitive types (Boolean, Number or String),
 *  node-sets or individual XML nodes.
 *  
 *
 *  
 *  When a variable is bound to a node-set, the
 *  actual Java object returned should be a java.util.List
 *  containing XML nodes from the object-model (dom4j, JDOM, DOM, EXML)
 *  being used with the XPath.
 *  
 *
 *  
 *  A variable may validly be assigned the null value,
 *  but an unbound variable (one that this context does not know about)
 *  should cause an {@link UnresolvableException} to be thrown.
 *  
 *
 *  @see SimpleVariableContext
 *  @see NamespaceContext
 *
 *  @author bob mcwhirter
 *  @author James Strachan
 */
public interface VariableContext
{
    /** An implementation should return the value of an xpath variable
     *  based on the namespace uri and local name of the variable-reference
     *  expression.
     *
     *  
     *  It must not use the prefix parameter to select a variable,
     *  because a prefix could be bound to any namespace; the prefix parameter
     *  could be used in debugging output or other generated information.
     *  The prefix may otherwise be ignored.
     *  
     *
     *  @param namespaceURI  the namespace uri to which the prefix parameter
     *                       is bound in the xpath expression. If the variable
     *                       reference expression had no prefix, the namespace
     *                       uri is null.
     *  @param prefix        the prefix that was used in the variable reference
     *                       expression.
     *  @param localName     the local name of the variable-reference
     *                       expression; if there is no prefix, then this is
     *                       the whole name of the variable.
     *
     *  @return  the variable's value (which can be null)
     *  @throws UnresolvableException  when the variable cannot be resolved.
     */
    public Object getVariableValue( String namespaceURI,
                                    String prefix,
                                    String localName )
        throws UnresolvableException;
}