package org.kuali.rice.krms.framework.engine;

 import java.util.List;

 import org.kuali.rice.krms.api.engine.Engine;

 import org.kuali.rice.krms.api.engine.ExecutionEnvironment;

 /**

  * Interface for logical propositions that may be executed in the {@link Engine}.

  * 

  * @author Kuali Rice Team (rice.collab@kuali.org)

  */

 public interface Proposition {

     /**

      * This method evaluates this proposition -- and in the case of {@link Proposition}s containing children,

      * those children as well -- and returns the boolean result; 

      * 

      * @param environment the {@link ExecutionEnvironment} that this {@link Proposition} is running in

      * @return the boolean result of evaluation

      */

         public PropositionResult evaluate(ExecutionEnvironment environment);

         /**

          * This method returns the {@link List} of child {@link Proposition}s that belong to this object.

          * If there are no children (e.g. for simple {@link Proposition} types), this must

          * return an empty {@link List}.

          * 

          * @return a {@link List} containing any child {@link Proposition}s that belong to this object.  Must never return null.

          */

         public List<Proposition> getChildren();

         /**

          * Indicates whether this {@link Proposition} can have children.

          * @return true if this {@link Proposition} can contain child {@link Proposition}s.

          */

         public boolean isCompound();

 }