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1   /*
2    * $Header$
3    * $Revision: 1261 $
4    * $Date: 2006-11-30 10:49:27 -0800 (Thu, 30 Nov 2006) $
5    *
6    * ====================================================================
7    *
8    * Copyright 2000-2002 bob mcwhirter & James Strachan.
9    * All rights reserved.
10   *
11   * Redistribution and use in source and binary forms, with or without
12   * modification, are permitted provided that the following conditions are
13   * met:
14   * 
15   *   * Redistributions of source code must retain the above copyright
16   *     notice, this list of conditions and the following disclaimer.
17   * 
18   *   * Redistributions in binary form must reproduce the above copyright
19   *     notice, this list of conditions and the following disclaimer in the
20   *     documentation and/or other materials provided with the distribution.
21   * 
22   *   * Neither the name of the Jaxen Project nor the names of its
23   *     contributors may be used to endorse or promote products derived 
24   *     from this software without specific prior written permission.
25   * 
26   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
27   * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
28   * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
29   * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
30   * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
31   * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
32   * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
33   * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
34   * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
35   * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
36   * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
37   *
38   * ====================================================================
39   * This software consists of voluntary contributions made by many 
40   * individuals on behalf of the Jaxen Project and was originally 
41   * created by bob mcwhirter <bob@werken.com> and 
42   * James Strachan <jstrachan@apache.org>.  For more information on the 
43   * Jaxen Project, please see <http://www.jaxen.org/>.
44   * 
45   * $Id: Expr.java 1261 2006-11-30 18:49:27Z elharo $
46   */
47  
48  
49  
50  package org.jaxen.expr;
51  
52  import java.io.Serializable;
53  import org.jaxen.Context;
54  import org.jaxen.JaxenException;
55  
56  /**
57   * Represents an XPath expression. This is production 14 in the 
58   * <a href="http://www.w3.org/TR/xpath#NT-Expr">XPath 1.0 specification</a>:
59   * 
60   * <pre>[14]      Expr       ::=      OrExpr</pre>
61   * 
62   */
63  public interface Expr extends Serializable
64  {
65      
66      
67      /**
68       * Returns a String containing the XPath expression.
69       * 
70       * @return the text form of this XPath expression
71       */
72      String getText();
73      
74      /**
75       * Simplifies the XPath expression. For example, the expression
76       * <code>//para[1 = 1]</code> could be simplified to 
77       * <code>//para</code>. In practice, this is usually a noop.
78       * Jaxen does not currently perform any simplification.
79       * 
80       * @return the simplified expression
81       */
82      Expr   simplify();
83      
84      
85      /**
86       * Evaluate the expression in the given context, and return the result.
87       * The result will be a <code>java.lang.Double</code> for expressions that 
88       * return a number, a <code>java.lang.String</code> for expressions that 
89       * return a string, a <code>java.lang.Boolean</code> for expressions that 
90       * return a boolean, and a <code>java.util.List</code> for expressions that
91       * return a node-set. In the latter case, the elements of the list are 
92       * the actual objects from the source document model. Copies are not made.
93       * 
94       * @param context the context in which the expression is evaluated
95       * @return an object representing the result of the evaluation
96       * @throws JaxenException
97       */
98      Object evaluate(Context context) throws JaxenException;
99      
100 }