我有一个严重的问题来启动和运行任何推理机。 还有文档中的示例:https://jena.apache.org/documentation/inference/ 在这里不起作用。 我将示例转移到单元测试中,这样问题可能更容易重现。
推理是否仅限于某些环境,如空间 JDK 等,还是我弄错了什么?
谢谢
这里是示例代码(作为 java 单元测试):
import static org.junit.Assert.assertNotNull;
import java.io.PrintWriter;
import java.util.Iterator;
import org.junit.Before;
import org.junit.Test;
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.Property;
import com.hp.hpl.jena.rdf.model.Resource;
import com.hp.hpl.jena.rdf.model.Statement;
import com.hp.hpl.jena.rdf.model.StmtIterator;
import com.hp.hpl.jena.reasoner.Derivation;
import com.hp.hpl.jena.reasoner.rulesys.GenericRuleReasoner;
import com.hp.hpl.jena.reasoner.rulesys.Rule;
import com.hp.hpl.jena.vocabulary.RDFS;
public class ReasonerTest {
String NS = "urn:x-hp-jena:eg/";
// Build a trivial example data set
Model model = ModelFactory.createDefaultModel();
InfModel inf;
Resource A = model.createResource(NS + "A");
Resource B = model.createResource(NS + "B");
Resource C = model.createResource(NS + "C");
Resource D = model.createResource(NS + "D");
Property p = model.createProperty(NS, "p");
Property q = model.createProperty(NS, "q");
@Before
public void init() {
// Some small examples (subProperty)
model.add(p, RDFS.subPropertyOf, q);
model.createResource(NS + "A").addProperty(p, "foo");
String rules = "[rule1: (?a eg:p ?b) (?b eg:p ?c) -> (?a eg:p ?c)]";
GenericRuleReasoner reasoner = new GenericRuleReasoner(Rule.parseRules(rules));
reasoner.setDerivationLogging(true);
inf = ModelFactory.createInfModel(reasoner, model);
// Derivations
A.addProperty(p, B);
B.addProperty(p, C);
C.addProperty(p, D);
}
@Test
public void subProperty() {
Statement statement = A.getProperty(q);
System.out.println("Statement: " + statement);
assertNotNull(statement);
}
@Test
public void derivations() {
String trace = null;
PrintWriter out = new PrintWriter(System.out);
for (StmtIterator i = inf.listStatements(A, p, D); i.hasNext(); ) {
Statement s = i.nextStatement();
System.out.println("Statement is " + s);
for (Iterator id = inf.getDerivation(s); id.hasNext(); ) {
Derivation deriv = (Derivation) id.next();
deriv.printTrace(out, true);
trace += deriv.toString();
}
}
out.flush();
assertNotNull(trace);
}
@Test
public void listStatements() {
StmtIterator stmtIterator = inf.listStatements();
while(stmtIterator.hasNext()) {
System.out.println(stmtIterator.nextStatement());
}
}
}
最佳答案
前缀 eg: 不是你想的那样:
eg:
规则中的前缀不会扩展到您认为的那样。我将您的规则字符串修改为
String rules = "[rule1: (?a eg:p ?b) (?b eg:p ?c) -> (?a eg:p ?c)] [rule2: -> (<urn:ex:a> eg:foo <urn:ex:b>)]";
因此 rule2 将始终将三元组 urn:ex:a eg:foo urn:ex:b 插入到图中。然后,测试的输出包括:
[urn:ex:a, urn:x-hp:eg/foo, urn:ex:b]
[urn:x-hp-jena:eg/C, urn:x-hp-jena:eg/p, urn:x-hp-jena:eg/D]
第一行显示我的 rule2 插入的三元组,而第二行使用您手动输入的前缀。我们看到 eg:
前缀是 urn:x-hp:eg/
的缩写.如果相应地更改 NS 字符串,请使用 String NS = "urn:x-hp:eg/";
,那么您的推导测试将通过。
你需要问正确的模型
subProperty 测试失败有两个原因。首先,它正在检查错误的模型。
您正在检查 A.getProperty(q)
:
Statement statement = A.getProperty(q);
System.out.println("Statement: " + statement);
assertNotNull(statement);
A
是您为模型创建的资源 model
,不是模型 inf
,所以当你要求 A.getProperty(q)
, 它实际上是在问 model
对于语句,因此您不会在 inf
中看到推论.您可以使用 inModel
得到A
“在 inf
中”所以 getProperty
寻找正确的模型:
Statement statement = A.inModel(inf).getProperty(q);
或者,您也可以询问 inf
直接是否包含 A q <something>
形式的三元组:
inf.contains( A, q, (RDFNode) null );
或者您可以枚举所有这样的语句:
StmtIterator stmts = inf.listStatements( A, q, (RDFNode) null );
assertTrue( stmts.hasNext() );
while ( stmts.hasNext() ) {
System.out.println( "Statement: "+stmts.next() );
}
你也需要RDFS推理
即使您正在查询正确的模型,您的推理模型仍然需要执行 RDFS 推理以及使属性 p 具有传递性的自定义规则。为此,我们可以从 RDFS 推理机中提取规则,将您的规则添加到该列表的副本中,然后使用新的规则列表创建自定义推理机:
// Get an RDFS reasoner
GenericRuleReasoner rdfsReasoner = (GenericRuleReasoner) ReasonerRegistry.getRDFSReasoner();
// Steal its rules, and add one of our own, and create a
// reasoner with these rules
List<Rule> customRules = new ArrayList<>( rdfsReasoner.getRules() );
String customRule = "[rule1: (?a eg:p ?b) (?b eg:p ?c) -> (?a eg:p ?c)]";
customRules.add( Rule.parseRule( customRule ));
Reasoner reasoner = new GenericRuleReasoner( customRules );
完整结果
这里是修改后的代码,全部放在一起方便复制和粘贴。所有测试均通过。
import static org.junit.Assert.assertNotNull;
import static org.junit.Assert.assertTrue;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import org.junit.Before;
import org.junit.Test;
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.Property;
import com.hp.hpl.jena.rdf.model.RDFNode;
import com.hp.hpl.jena.rdf.model.Resource;
import com.hp.hpl.jena.rdf.model.Statement;
import com.hp.hpl.jena.rdf.model.StmtIterator;
import com.hp.hpl.jena.reasoner.Derivation;
import com.hp.hpl.jena.reasoner.Reasoner;
import com.hp.hpl.jena.reasoner.ReasonerRegistry;
import com.hp.hpl.jena.reasoner.rulesys.GenericRuleReasoner;
import com.hp.hpl.jena.reasoner.rulesys.Rule;
import com.hp.hpl.jena.vocabulary.RDFS;
public class ReasonerTest {
String NS = "urn:x-hp:eg/";
// Build a trivial example data set
Model model = ModelFactory.createDefaultModel();
InfModel inf;
Resource A = model.createResource(NS + "A");
Resource B = model.createResource(NS + "B");
Resource C = model.createResource(NS + "C");
Resource D = model.createResource(NS + "D");
Property p = model.createProperty(NS, "p");
Property q = model.createProperty(NS, "q");
@Before
public void init() {
// Some small examples (subProperty)
model.add(p, RDFS.subPropertyOf, q);
A.addProperty(p, "foo" );
// Get an RDFS reasoner
GenericRuleReasoner rdfsReasoner = (GenericRuleReasoner) ReasonerRegistry.getRDFSReasoner();
// Steal its rules, and add one of our own, and create a
// reasoner with these rules
List<Rule> customRules = new ArrayList<>( rdfsReasoner.getRules() );
String customRule = "[rule1: (?a eg:p ?b) (?b eg:p ?c) -> (?a eg:p ?c)]";
customRules.add( Rule.parseRule( customRule ));
Reasoner reasoner = new GenericRuleReasoner( customRules );
reasoner.setDerivationLogging(true);
inf = ModelFactory.createInfModel(reasoner, model);
// Derivations
A.addProperty(p, B);
B.addProperty(p, C);
C.addProperty(p, D);
}
@Test
public void subProperty() {
StmtIterator stmts = inf.listStatements( A, q, (RDFNode) null );
assertTrue( stmts.hasNext() );
while ( stmts.hasNext() ) {
System.out.println( "Statement: "+stmts.next() );
}
}
@Test
public void derivations() {
String trace = null;
PrintWriter out = new PrintWriter(System.out);
for (StmtIterator i = inf.listStatements(A, p, D); i.hasNext(); ) {
Statement s = i.nextStatement();
System.out.println("Statement is " + s);
for (Iterator<Derivation> id = inf.getDerivation(s); id.hasNext(); ) {
Derivation deriv = (Derivation) id.next();
deriv.printTrace(out, true);
trace += deriv.toString();
}
}
out.flush();
assertNotNull(trace);
}
@Test
public void listStatements() {
StmtIterator stmtIterator = inf.listStatements();
while(stmtIterator.hasNext()) {
System.out.println(stmtIterator.nextStatement());
}
}
}
关于java - 来自 Apache Jena 框架的推理示例的问题,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/24786035/