semanticssupport.java

Mandarax是一个规则引擎的纯Java实现。它支持多类型的事实和基于反映的规则

/*
 * Copyright (C) 1999-2004 <A href="http://www-ist.massey.ac.nz/JBDietrich" target="_top">Jens Dietrich</a>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
package org.mandarax.kernel;


/**
 * Interface for objects that may support semantic evaluation.
 * E.g., a term 'plus(2,3)' with the plus function from the mandarax integer
 * lib and the two constant terms wrapping the Integer instances 2 and 3
 * can be evaluated (performed) using the semantics of the respective java operator
 * or method, the evaluation will yield 5 (or more precisely, a constant
 * term wrapping the Integer instance 5).
 * <br>
 * In a similar manner, a fact such as 4&ltplus(2,3) can be evaluated, the result is
 * a boolean (true in this case). On the other hand, a term like plus(2,x) or a term
 * like 4&ltplus(2,x) (with x being a variable term) cannot be evaluated, besides the class
 * AutoFacts class provides a certain generalization for this case.
 * <br>
 * The kind of semantic used depends on the object. Since we use java as a platform,
 * at the end it is always the meaning objects have through the implementation of
 * their classes. Somethimes, the actual computation might be deligated to other systems,
 * like to the relational model in case of functions integrating SQL databases,
 * or to C++ objects in case of functions and predicates using CORBA.
 * @see org.mandarax.util.AutoFacts
 * @see org.mandarax.sql.SQLFunction
 * @see org.mandarax.sql.SQLPredicate
 * @see org.mandarax.kernel.meta.JFunction
 * @see org.mandarax.kernel.meta.JPredicate
 * @author <A href="http://www-ist.massey.ac.nz/JBDietrich" target="_top">Jens Dietrich</A>
 * @version 3.4 <7 March 05>
 * @since 1.6
 */
public interface SemanticsSupport {

    /**
     * Indicates whether the object (usually a term or a clause set) can be performed
     * using the java semantics.
     * @return a boolean
     */
    public boolean isExecutable();
}