为什么会发生这种异常com.hp.hpl.jena.reasoner.rulesys.Rule $ ParserException:在使用Apache Jena推理器?

时间:2017-02-16 05:59:41

标签: java jena apache-jena jena-rules

这是我的代码:

public class FunctionalityCheckTest1 {

    InfModel infModel;
    Model model = ModelFactory.createDefaultModel();
    String NS = "http://myweb.com/vocab#";

    @Test
    public void playingWithJenaReasoner()
    {
        Resource alex = this.model.createResource(NS+"Alex");
        Resource bob = this.model.createResource(NS+"Bob");
        Resource alice = this.model.createResource(NS+"Alice");
        Property isFriendOf = this.model.createProperty(NS,"isFriendOf");
        alex.addProperty(isFriendOf,bob);
        bob.addProperty(isFriendOf,alice);
        StmtIterator stmtIterator1 = this.model.listStatements();
        while (stmtIterator1.hasNext())
        {
            System.out.println(stmtIterator1.next());
        }

        String customRule = "@prefix vocab: <http://myweb.com/vocab#>. " +
                "[rule1: (?a vocab:isFriendOf ?b) (?b vocab:isFriendOf ?c) -> (?a vocab:isFriendOf ?c) ]";

        List<Rule> rules = new ArrayList<>();
        rules.add(Rule.parseRule(customRule));

        GenericRuleReasoner reasoner = new GenericRuleReasoner(rules);
        reasoner.setDerivationLogging(false);
        this.infModel = ModelFactory.createInfModel(reasoner, this.model);
        StmtIterator stmtIterator2 = this.infModel.listStatements();
        while (stmtIterator2.hasNext())
        {
            System.out.println(stmtIterator2.next());
        }
    }

}

在执行playingWithJenaReasoner()函数时,它会抛出错误:
com.hp.hpl.jena.reasoner.rulesys.Rule $ ParserException:预期&#39;(&#39;在条款开头,找到词汇:
来自行规则.add (Rule.parseRule(customRule));

如果我将这些更改添加到上面的代码中,一切正常

PrintUtil.registerPrefix("vocab",NS);
String customRule = "[rule1: (?a vocab:isFriendOf ?b) (?b vocab:isFriendOf ?c) -> (?a vocab:isFriendOf ?c) ]";

这个怎么回事?

String customRule = "@prefix vocab: <http://myweb.com/vocab#>. " +
                    "[rule1: (?a vocab:isFriendOf ?b) (?b vocab:isFriendOf ?c) -> (?a vocab:isFriendOf ?c) ]";

在这个Jena Documentation中,他们提到了@prefix with rule。我哪里做错了?

1 个答案:

答案 0 :(得分:2)

我遇到了你今天遇到的同样的问题,这似乎是方法

public static List<Rule> parseRules(String source)

不允许字符串中包含前缀。我不确定这是否是此方法的错误或功能。

但是,如果您在规则文件中声明规则并通过

加载它

public static List<Rule> rulesFromURL(String uri)

您应该能够加载包含前缀的规则。

这是一个测试是否有效的小例子。它假定您将本体存储在文件系统的某个位置,并在类路径中包含名为jena.rule的规则文件:

public class JenaRuleTest {

    public static void main(String[] args) throws UnsupportedEncodingException {

        OntModel model = ModelFactory.createOntologyModel();        
        model.read("C:\\path\\to\\ontology\\ontology.ttl");     

        String ruleResourceStr = JenaRuleTest.class.getResource("/jena.rule").toString();

        Reasoner reasoner = new GenericRuleReasoner(Rule.rulesFromURL(ruleResourceStr));
        reasoner.setDerivationLogging(true);

        InfModel inf = ModelFactory.createInfModel(reasoner, model);        
        inf.write(System.out, "TURTLE");        
    }
}

更详细的示例如何在此处找到:http://tutorial-academy.com/jena-reasoning-with-rules/

Rule课程的文档可在此处找到:https://jena.apache.org/documentation/javadoc/jena/org/apache/jena/reasoner/rulesys/Rule.html

希望如果有人遇到这个问题会有所帮助。

问候