这是我编写的代码，但新的内置似乎不起作用。我收到错误：
线程中的异常“main”com.hp.hpl.jena.reasoner.rulesys.impl.LPRuleSyntaxException：向后规则中的语法错误：matematica未知的内置操作mysum
谁能告诉我错误在哪里？这是我的代码：
package JenaRules;
import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Arrays;
import java.util.List;
import org.semanticweb.owlapi.model.OWLOntologyCreationException;
import org.semanticweb.owlapi.model.OWLOntologyStorageException;
import com.hp.hpl.jena.graph.Node;
import com.hp.hpl.jena.query.Query;
import com.hp.hpl.jena.query.QueryExecution;
import com.hp.hpl.jena.query.QueryExecutionFactory;
import com.hp.hpl.jena.query.QueryFactory;
import com.hp.hpl.jena.query.ResultSet;
import com.hp.hpl.jena.query.ResultSetFormatter;
import com.hp.hpl.jena.rdf.model.InfModel;
import com.hp.hpl.jena.rdf.model.Model;
import com.hp.hpl.jena.rdf.model.ModelFactory;
import com.hp.hpl.jena.rdf.model.Resource;
import com.hp.hpl.jena.reasoner.Reasoner;
import com.hp.hpl.jena.reasoner.rulesys.*;
import com.hp.hpl.jena.reasoner.rulesys.builtins.BaseBuiltin;
import com.hp.hpl.jena.util.FileManager;
import com.hp.hpl.jena.vocabulary.RDFS;
import com.hp.hpl.jena.vocabulary.ReasonerVocabulary;
public class RulesOntology_MT {
public static void main(String[] args) throws OWLOntologyStorageException,
OWLOntologyCreationException, IOException {
BuiltinRegistry.theRegistry.register(new BaseBuiltin() {
@Override
public String getName() {
return "mysum";
}
@Override
public int getArgLength() {
return 2;
}
@Override
public boolean bodyCall(Node[] args, int length, RuleContext context) {
checkArgs(length, context);
BindingEnvironment env = context.getEnv();
Node n1 = getArg(0, args, context);
Node n2 = getArg(1, args, context);
if (n1.isLiteral() && n2.isLiteral()) {
Object v1 = n1.getLiteralValue();
Object v2 = n2.getLiteralValue();
Node sum = null;
if (v1 instanceof Number && v2 instanceof Number) {
Number nv1 = (Number)v1;
Number nv2 = (Number)v2;
int sumInt = nv1.intValue()+nv2.intValue();
sum = Util.makeIntNode(sumInt);
return env.bind(args[2], sum);
}
}
return false;
}
});
// NON SERVE
// final String exampleRuleString2 =
// "[mat1: equal(?s ?p )\n\t-> print(?s ?p ?o),\n\t (?s ?p ?o)\n]"+
// "";
final String exampleRuleString =
"[matematica:"+
"(?p http://www.semanticweb.org/prova_rules_M#totale_crediti ?x)"+
" -> " +
"(?p rdf:type http://www.semanticweb.org/prova_rules_M#:Persona)"+
"(?e rdf:type http://www.semanticweb.org/prova_rules_M#:Esame)"+
"(?p http://www.semanticweb.org/prova_rules_M#:haSostenutoEsameDi ?e)"+
"(?e http://www.semanticweb.org/prova_rules_M/persona#crediti_esame ?cr)"+
"mysum(?cr,2)"+
"]";
System.out.println(exampleRuleString);
/* I tend to use a fairly verbose syntax for parsing out my rules when I construct them
* from a string. You can read them from whatever other sources.
*/
final List<Rule> rules;
try( final BufferedReader src = new BufferedReader(new InputStreamReader(new ByteArrayInputStream(exampleRuleString.getBytes()))) ) {
rules = Rule.parseRules(Rule.rulesParserFromReader(src));
}
/* Construct a reasoner and associate the rules with it */
// create an empty non-inferencing model
GenericRuleReasoner reasoner = (GenericRuleReasoner) GenericRuleReasonerFactory.theInstance().create(null);
reasoner.setRules(rules);
/* Create & Prepare the InfModel. If you don't call prepare, then
* rule firings and inference may be deferred until you query the
* model rather than happening at insertion. This can make you think
* that your Builtin is not working, when it is.
*/
InfModel infModel = ModelFactory.createInfModel(reasoner, ModelFactory.createDefaultModel());
infModel.prepare();
infModel.createResource(RDFS.Class);
//write down the result in RDFXML form
infModel.write(System.out);
}
}
答案 0 :(得分：0)
使用您提供的代码和Apache Jena 2.11.1，我无法复制您获得的异常。请注意，当您致电BuiltinRegistry.theRegistry.register(...)时，您 告诉推理人内置网存在。
<强>解决方案
您 获取的例外可能是因为，在您的实际代码中，您在调用BuiltinRegistry.theRegistry.register(...)之前没有调用Rule.parseRules(Rule.rulesParserFromReader(src));，因此，就规则解析器而言，您使用的是不存在的Builtin。要修复它，只需在解析规则之前调用register。提供的玩具示例没有这个问题。
使用提供的示例
我还注意到，提供的代码示例中没有包含任何会刺激规则的内容，因此，代替infModel.createResource(RDFS.Class);，我添加了以下几行：
final Resource s = infModel.createResource();
final Property p = infModel.createProperty("http://www.semanticweb.org/prova_rules_M#totale_crediti");
final Resource o = infModel.createResource();
infModel.add(s,p,o);
这刺激了规则的触发，并导致以下异常追踪：
com.hp.hpl.jena.reasoner.rulesys.BuiltinException: Error in clause of rule (matematica) mysum: builtin mysum not usable in rule heads
at com.hp.hpl.jena.reasoner.rulesys.builtins.BaseBuiltin.headAction(BaseBuiltin.java:86)
at com.hp.hpl.jena.reasoner.rulesys.impl.RETEConflictSet.execute(RETEConflictSet.java:184)
at com.hp.hpl.jena.reasoner.rulesys.impl.RETEConflictSet.add(RETEConflictSet.java:81)
at com.hp.hpl.jena.reasoner.rulesys.impl.RETEEngine.requestRuleFiring(RETEEngine.java:249)
at com.hp.hpl.jena.reasoner.rulesys.impl.RETETerminal.fire(RETETerminal.java:80)
at com.hp.hpl.jena.reasoner.rulesys.impl.RETEClauseFilter.fire(RETEClauseFilter.java:227)
at com.hp.hpl.jena.reasoner.rulesys.impl.RETEEngine.inject(RETEEngine.java:469)
at com.hp.hpl.jena.reasoner.rulesys.impl.RETEEngine.runAll(RETEEngine.java:451)
at com.hp.hpl.jena.reasoner.rulesys.impl.RETEEngine.add(RETEEngine.java:174)
at com.hp.hpl.jena.reasoner.rulesys.FBRuleInfGraph.performAdd(FBRuleInfGraph.java:654)
at com.hp.hpl.jena.graph.impl.GraphBase.add(GraphBase.java:202)
at com.hp.hpl.jena.rdf.model.impl.ModelCom.add(ModelCom.java:1138)
at SO.test(SO.java:108)
作为备注：我的测试类为SO.java，第108行是我们称之为infModel.add(s,p,o)的位置。
我得到的异常与您遇到的异常不同，但值得解释。您提供的实现实现Builtin#bodyCall(...)，但不实现Builtin#headAction(...)。我们可以看到BaseBuiltin#headAction(...)抛出异常。此默认行为假定您未实现该方法，因为Builtin不支持该方法。在玩具问题中，这是正确的行为，因为示例实现不能在规则头中使用。