/*
* 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.builtins;
import org.apache.jena.graph.* ;
import org.apache.jena.reasoner.rulesys.* ;
/**
* Dummy implementation of the Builtin interface that specific
* implementations can inherit from.
*/
public abstract class BaseBuiltin implements Builtin {
/** Base URI for jena builtins */
public static final String BASE_URI = "http://jena.hpl.hp.com/2003/RuleBuiltin/";
/**
* Return the full URI which identifies this built in.
*/
@Override
public String getURI() {
return BASE_URI + getName();
}
/**
* Return the expected number of arguments for this functor or 0 if the number is flexible.
*/
@Override
public int getArgLength() {
return 0;
}
/**
* Check the argument length.
*/
public void checkArgs(int length, RuleContext context) {
int expected = getArgLength();
if (expected > 0 && expected != length) {
throw new BuiltinException(this, context, "builtin " + getName() + " requires " + expected + " arguments but saw " + length);
}
}
/**
* 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
*/
@Override
public boolean bodyCall(Node[] args, int length, RuleContext context) {
throw new BuiltinException(this, context, "builtin " + getName() + " not usable in rule bodies");
}
/**
* 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
*/
@Override
public void headAction(Node[] args, int length, RuleContext context) {
throw new BuiltinException(this, context, "builtin " + getName() + " not usable in rule heads");
}
/**
* Returns false if this builtin has side effects when run in a body clause,
* other than the binding of environment variables.
*/
@Override
public boolean isSafe() {
// Default is safe!
return true;
}
/**
* 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.
*/
@Override
public boolean isMonotonic() {
return true;
}
/**
* Return the n'th argument node after dererencing by what ever type of
* rule engine binding environment is appropriate.
*/
public Node getArg(int n, Node[] args, RuleContext context) {
return context.getEnv().getGroundVersion(args[n]);
}
}