在耶拿解释推理

Question

在耶拿，我使用 InfModel 类创建了一个 RDFS 推理模型：

InfModel infmodel = ModelFactory.createRDFSModel(schema, data);

给定一个来自 infmodel 的推断语句，我们如何获得用于推断它的两个语句，类似于 Protégé 中的“解释推断”选项？例如，如果infModel 包含语句:a rdf:type :t，我们可能会得到两个用于推断它的语句，例如:a :p :b 和:p rdfs:domain :t。

Answer 1

根据the documentation（并使用Jena 2.11.1 进行测试），您可以访问Derivation 对象，该对象将允许您创建对所发生事件的文本描述。在以下示例中，我们检索RuleDerivation 对象，这些对象公开了更多关于内部状态的信息。

以下是文档示例的经过测试的实现，它以以下模型开头：

<urn:eg:C>  <urn:eg:p>  <urn:eg:D> .
<urn:eg:B>  <urn:eg:p>  <urn:eg:C> .
<urn:eg:A>  <urn:eg:p>  <urn:eg:B> .

...以及以下规则：

[rule1: (?a urn:eg:p ?b) (?b urn:eg:p ?c) -> (?a urn:eg:p ?c)]

...生成这个结果模型：

<urn:eg:B>  <urn:eg:p>  <urn:eg:D> , <urn:eg:C> .
<urn:eg:A>  <urn:eg:p>  <urn:eg:D> , <urn:eg:C> , <urn:eg:B> .
<urn:eg:C>  <urn:eg:p>  <urn:eg:D> .

这个基本的传递推理成为下面示例的核心方面。请注意，我们获得了一个 RuleDerivation 的实例，这是您实现最终目标的开始。

final Resource A = ResourceFactory.createResource("urn:eg:A");
final Resource B = ResourceFactory.createResource("urn:eg:B");
final Resource C = ResourceFactory.createResource("urn:eg:C");
final Resource D = ResourceFactory.createResource("urn:eg:D");
final Property p = ResourceFactory.createProperty("urn:eg:p");

final Model rawData = ModelFactory.createDefaultModel();
rawData.add(A, p, B);
rawData.add(B, p, C);
rawData.add(C, p, D);

final String rules = "[rule1: (?a urn:eg:p ?b) (?b urn:eg:p ?c) -> (?a urn:eg:p ?c)]";
final Reasoner reasoner = new GenericRuleReasoner(Rule.parseRules(rules));
reasoner.setDerivationLogging(true);
final InfModel inf = ModelFactory.createInfModel(reasoner, rawData);

final 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 (final Iterator<Derivation> id = inf.getDerivation(s); id.hasNext(); ) {
        final RuleDerivation deriv = (RuleDerivation) id.next();
        deriv.printTrace(out, true);
    }
}
out.flush();

这个例子的输出是：

Statement is [urn:eg:A, urn:eg:p, urn:eg:D]
Rule rule1 concluded (urn:eg:A urn:eg:p urn:eg:D) <-
    Rule rule1 concluded (urn:eg:A urn:eg:p urn:eg:C) <-
        Fact (urn:eg:A urn:eg:p urn:eg:B)
        Fact (urn:eg:B urn:eg:p urn:eg:C)
    Fact (urn:eg:C urn:eg:p urn:eg:D)

编辑 - 提示

如果您正在寻找有关如何探索推导的示例，请查看 RuleDerivation#printTrace(...) 的内部结构。如果要将三元组（从 RuleDerivation#getMatches()）转换回语句，请使用 StatementImpl#toStaetment(Triple,ModelCom)。

EDIT2 - 完成 假设您使用的是 Jena 内置的基于规则的推理器之一，以下代码将允许您探索推理器报告的特定推导的匹配项。

final StmtIterator input = inf.listStatements(A, p, D);
assert( input.hasNext() );

final Iterator<Derivation> derivations = inf.getDerivation(input.next());
assert( null != derivations );
assert( derivations.hasNext() );

final RuleDerivation oneDerivation = (RuleDerivation) derivations.next();
final ExtendedIterator< Statement > matches = 
        new NiceIterator< Triple >()
        .andThen( oneDerivation.getMatches().iterator())
        .mapWith( new Map1< Triple, Statement >(){
            @Override
            public Statement map1( final Triple t )
            {
                /* Note that it seems that this model doesn't really mean anything. While
                 * the statement will be associated with the infModel, the triple that led
                 * to the match could have been from either the deductions graph or the
                 * raw graph. This does not actually add any triples to the underlying
                 * store.
                 */
                return StatementImpl.toStatement(t, (ModelCom)inf);
            }});