/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.jena.reasoner.rulesys;
import org.apache.jena.graph.* ;
/**
* Rules employ builtins to do all tests and actions other than simple triple
* matches and triple creation.
* <p>
* Builtins can be invoked in two contexts. In the head of forward rules they perform
* some action based on the variable bindings generated by the body and additional context
* (the graph being reasoned over, the set of triples bound by the body). In the body
* of rules they perform tests, and additional variable bindings.
* <p>
* The mapping from the rule definition (which uses functors to hold the parsed call)
* to the java implementation of the builtin is done via the
* {@link MapBuiltinRegistry BuiltinRegistry} which can
* be user extended.
*/
public interface Builtin {
/**
* Return a convenient name for this builtin, normally this will be the name of the
* functor that will be used to invoke it and will often be the final component of the
* URI.
*/
public String getName();
/**
* Return the full URI which identifies this built in.
*/
public String getURI();
/**
* Return the expected number of arguments for this functor or 0 if the number is flexible.
*/
public int getArgLength();
/**
* This method is invoked when the builtin is called in a rule body.
* @param args the array of argument values for the builtin, this is an array
* of Nodes, some of which may be Node_RuleVariables.
* @param length the length of the argument list, may be less than the length of the args array
* for some rule engines
* @param context an execution context giving access to other relevant data
* @return return true if the buildin predicate is deemed to have succeeded in
* the current environment
*/
public boolean bodyCall(Node[] args, int length, RuleContext context);
/**
* This method is invoked when the builtin is called in a rule head.
* Such a use is only valid in a forward rule.
* @param args the array of argument values for the builtin, this is an array
* of Nodes.
* @param length the length of the argument list, may be less than the length of the args array
* for some rule engines
* @param context an execution context giving access to other relevant data
*/
public void headAction(Node[] args, int length, RuleContext context);
/**
* Returns false if this builtin has side effects when run in a body clause,
* other than the binding of environment variables.
*/
public boolean isSafe();
/**
* Returns false if this builtin is non-monotonic. This includes non-monotonic checks like noValue
* and non-monotonic actions like remove/drop. A non-monotonic call in a head is assumed to
* be an action and makes the overall rule and ruleset non-monotonic.
* Most JenaRules are monotonic deductive closure rules in which this should be false.
*/
public boolean isMonotonic();
}