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1   /*
2    *
3    *   Copyright 2005 The Apache Software Foundation.
4    *
5    *  Licensed under the Apache License, Version 2.0 (the "License");
6    *  you may not use this file except in compliance with the License.
7    *  You may obtain a copy of the License at
8    *
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   *
11   *  Unless required by applicable law or agreed to in writing, software
12   *  distributed under the License is distributed on an "AS IS" BASIS,
13   *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   *  See the License for the specific language governing permissions and
15   *  limitations under the License.
16   *
17   */
18  package org.apache.commons.scxml;
19  
20  import org.w3c.dom.Node;
21  
22  /***
23   * Interface for a component that may be used by the SCXML engines to
24   * evaluate the expressions within the SCXML document.
25   *
26   */
27  public interface Evaluator {
28  
29      /***
30       * Evaluate an expression.
31       *
32       * @param ctx variable context
33       * @param expr expression
34       * @return a result of the evaluation
35       * @throws SCXMLExpressionException A malformed exception
36       */
37      Object eval(Context ctx, String expr)
38      throws SCXMLExpressionException;
39  
40      /***
41       * Evaluate a condition.
42       * Manifests as "cond" attributes of <transition>,
43       * <if> and <elseif> elements.
44       *
45       * @param ctx variable context
46       * @param expr expression
47       * @return true/false
48       * @throws SCXMLExpressionException A malformed exception
49       */
50      Boolean evalCond(Context ctx, String expr)
51      throws SCXMLExpressionException;
52  
53      /***
54       * Evaluate a location that returns a Node within an XML data tree.
55       * Manifests as "location" attributes of <assign> element.
56       *
57       * @param ctx variable context
58       * @param expr expression
59       * @return The location node.
60       * @throws SCXMLExpressionException A malformed exception
61       */
62      Node evalLocation(Context ctx, String expr)
63      throws SCXMLExpressionException;
64  
65      /***
66       * Create a new child context.
67       *
68       * @param parent parent context
69       * @return new child context
70       */
71      Context newContext(Context parent);
72  
73  }
74