001/**
002 * Copyright 2005-2014 The Kuali Foundation
003 *
004 * Licensed under the Educational Community License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 * http://www.opensource.org/licenses/ecl2.php
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016package org.kuali.rice.krms.framework.engine;
017
018import java.util.List;
019
020import org.kuali.rice.krms.api.engine.Engine;
021import org.kuali.rice.krms.api.engine.ExecutionEnvironment;
022
023/**
024 * Interface for logical propositions that may be executed in the {@link Engine}.
025 * @see PropositionResult
026 * @author Kuali Rice Team (rice.collab@kuali.org)
027 */
028public interface Proposition {
029
030    /**
031     * Evaluates this proposition -- and in the case of {@link Proposition}s containing children,
032     * those children as well -- and returns the boolean result; 
033     * 
034     * @param environment the {@link ExecutionEnvironment} that this {@link Proposition} is running in
035     * @return the boolean result of evaluation
036     */
037        public PropositionResult evaluate(ExecutionEnvironment environment);
038        
039        /**
040         * Returns the {@link List} of child {@link Proposition}s that belong to this object.
041         * If there are no children (e.g. for simple {@link Proposition} types), this must
042         * return an empty {@link List}.
043         * 
044         * @return a {@link List} containing any child {@link Proposition}s that belong to this object.  Must never return null.
045         */
046        public List<Proposition> getChildren();
047        
048        /**
049         * Indicates whether this {@link Proposition} can have children.
050         * @return true if this {@link Proposition} can contain child {@link Proposition}s.
051         */
052        public boolean isCompound();
053                
054}