001 // Copyright 2004, 2005 The Apache Software Foundation 002 // 003 // Licensed under the Apache License, Version 2.0 (the "License"); 004 // you may not use this file except in compliance with the License. 005 // You may obtain a copy of the License at 006 // 007 // http://www.apache.org/licenses/LICENSE-2.0 008 // 009 // Unless required by applicable law or agreed to in writing, software 010 // distributed under the License is distributed on an "AS IS" BASIS, 011 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 012 // See the License for the specific language governing permissions and 013 // limitations under the License. 014 015 package org.apache.hivemind.conditional; 016 017 /** 018 * An evaluator is paired with a {@link Node}. The Node provides structure, the Evaluator provides 019 * meaning, interpreting the node. 020 * 021 * @author Howard M. Lewis Ship 022 * @since 1.1 023 */ 024 public interface Evaluator 025 { 026 /** 027 * Invoked by the Node to evaluate its own value. Typical implementations will extract the 028 * Node's {@link org.apache.hivemind.conditional.Node#getLeft() left} and 029 * {@link org.apache.hivemind.conditional.Node#getRight() right} properties and combine or 030 * otherwise evaluate them. Terminal nodes in the tree will have evaluators that don't do that 031 * but generate a return value internally. 032 */ 033 034 public boolean evaluate(EvaluationContext context, Node node); 035 }