Jena TDB 101 Java API without Assembler
Update on 2015/05/12
ongoing tutorials site on https://github.com/zhoujiagen/semanticWebTutorialUsingJena
废话
/** 前几天的面试，是一个组织研究生团队开展分布式计算应用的面试。在该面试中，被虐的很惨，在这里整理一下一些重要的反馈： (1)什么是本体、语义Web？有没有什么应用市场？ 第一遍回答的支离破碎的，之后面试官是在看不下去，诱导性的说举个例子吧，才回答出概念taxonomy、概念关系和关系推理等内容。 至于应用市场直接回答没有考虑过，面试官提醒可以在搜索引擎中应用，哎，专业性都受到严重的质疑。 (2) 目前做过的简单Java开发已经有廉价的工具优雅的替代了。 这部分不想多说，连我自己都认为是这样，我也不想当个“廉价的”J2EE开发工程师。因简历上hadoop、hbase前面我写的是了解，只问了一下有没有装过hadoop，确实是装过0.x版本的伪分布式模式的。 这一系列语义网的随笔确实是为体现专业性而写的，之前OntoABAC原型系统中用到的技术是可以演示毕业论文中的论点的，但完全无法达到研究前沿和应用级别的要求。 据我所知，语义网的前沿是在其层次体系结构中上层的proof和trust，而应用级别又要求满足低成本、大数据量和结合计算架构的开发。 长城不是一夜间堆完的，革命尚未成功，自己仍需努力；多暴露自己的不足、多问几个为什么，尽力完善专业性知识。 */
前言
RDF中数据，尤其是实例断言的数据量很大时，该怎么处理？采用老而弥坚的关系型数据库？还是使用其他模型的存储？
Jena本身支持SDB(http://jena.apache.org/documentation/sdb/)，支持RDF数据在关系型数据库中的存储，但其页面中也提出不建议使用这种方式。有兴趣的可以去看Oracle的语义技术开发者指南。
本文以一个示例展示如何在TDB中以编程方式实现RDF数据的存储和访问，不涉及assembler。
内容
1 数据！
2 创建Dataset、加载数据
3 查询数据
4 遗留问题
1 数据！
exploration.owl - 导入FOAF.rdf，添加了部分概念、实例、关系和一个SWRL规则
<?xml version="1.0"?>
<!DOCTYPE rdf:RDF [
<!ENTITY foaf "http://xmlns.com/foaf/0.1/" >
<!ENTITY owl "http://www.w3.org/2002/07/owl#" >
<!ENTITY swrl "http://www.w3.org/2003/11/swrl#" >
<!ENTITY swrlb "http://www.w3.org/2003/11/swrlb#" >
<!ENTITY xsd "http://www.w3.org/2001/XMLSchema#" >
<!ENTITY rdfs "http://www.w3.org/2000/01/rdf-schema#" >
<!ENTITY rdf "http://www.w3.org/1999/02/22-rdf-syntax-ns#" >
]>
<rdf:RDF xmlns="http://www.jena.application.com/exploration#"
xml:base="http://www.jena.application.com/exploration"
xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#"
xmlns:swrl="http://www.w3.org/2003/11/swrl#"
xmlns:foaf="http://xmlns.com/foaf/0.1/"
xmlns:owl="http://www.w3.org/2002/07/owl#"
xmlns:xsd="http://www.w3.org/2001/XMLSchema#"
xmlns:swrlb="http://www.w3.org/2003/11/swrlb#"
xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
<owl:Ontology rdf:about="http://www.jena.application.com/exploration">
<owl:versionIRI rdf:resource="http://www.jena.application.com/exploration/1.0"/>
<owl:imports rdf:resource="http://xmlns.com/foaf/0.1/"/>
</owl:Ontology>
<!--
///////////////////////////////////////////////////////////////////////////////////////
//
// Data properties
//
///////////////////////////////////////////////////////////////////////////////////////
-->
<!-- http://www.jena.application.com/exploration#mbox -->
<owl:DatatypeProperty rdf:about="http://www.jena.application.com/exploration#mbox"/>
<!--
///////////////////////////////////////////////////////////////////////////////////////
//
// Classes
//
///////////////////////////////////////////////////////////////////////////////////////
-->
<!-- http://www.jena.application.com/exploration#GmailPerson -->
<owl:Class rdf:about="http://www.jena.application.com/exploration#GmailPerson"/>
<!--
///////////////////////////////////////////////////////////////////////////////////////
//
// Individuals
//
///////////////////////////////////////////////////////////////////////////////////////
-->
<!-- http://www.jena.application.com/exploration#Ontology -->
<owl:NamedIndividual rdf:about="http://www.jena.application.com/exploration#Ontology">
<rdf:type rdf:resource="http://schema.org/Person"/>
<foaf:name rdf:datatype="&xsd;string">I. M. Ontology</foaf:name>
<rdfs:seeAlso rdf:datatype="&xsd;string">http://ont.com
</rdfs:seeAlso>
<mbox rdf:datatype="&xsd;string">onto@gmail.com</mbox>
</owl:NamedIndividual>
<!-- http://www.jena.application.com/exploration#Reasoner -->
<owl:NamedIndividual rdf:about="http://www.jena.application.com/exploration#Reasoner">
<rdf:type rdf:resource="http://schema.org/Person"/>
<foaf:name rdf:datatype="&xsd;string">Ican Reason</foaf:name>
<rdfs:seeAlso rdf:datatype="&xsd;string">http://reasoner.com</rdfs:seeAlso>
<mbox rdf:datatype="&xsd;string">reason@hotmail.com</mbox>
</owl:NamedIndividual>
<!-- http://www.jena.application.com/exploration#Statement -->
<owl:NamedIndividual rdf:about="http://www.jena.application.com/exploration#Statement">
<rdf:type rdf:resource="http://schema.org/Person"/>
<foaf:name rdf:datatype="&xsd;string">Makea Statement</foaf:name>
<rdfs:seeAlso rdf:datatype="&xsd;string">http://statement.com</rdfs:seeAlso>
<mbox rdf:datatype="&xsd;string">mstatement@gmail.com</mbox>
</owl:NamedIndividual>
<!-- http://www.jena.application.com/exploration#me -->
<owl:NamedIndividual rdf:about="http://www.jena.application.com/exploration#me">
<rdf:type rdf:resource="http://schema.org/Person"/>
<foaf:name rdf:datatype="&xsd;string">Zhou Jia-Gen</foaf:name>
<mbox rdf:datatype="&xsd;string">zhoujiagen@gmail.com</mbox>
<foaf:knows rdf:resource="http://www.jena.application.com/exploration#Ontology"/>
<foaf:knows rdf:resource="http://www.jena.application.com/exploration#Reasoner"/>
<foaf:knows rdf:resource="http://www.jena.application.com/exploration#Statement"/>
</owl:NamedIndividual>
<!--
///////////////////////////////////////////////////////////////////////////////////////
//
// Rules
//
///////////////////////////////////////////////////////////////////////////////////////
-->
<rdf:Description rdf:about="urn:swrl#p">
<rdf:type rdf:resource="&swrl;Variable"/>
</rdf:Description>
<rdf:Description rdf:about="urn:swrl#m">
<rdf:type rdf:resource="&swrl;Variable"/>
</rdf:Description>
<rdf:Description>
<rdf:type rdf:resource="&swrl;Imp"/>
<swrl:body>
<rdf:Description>
<rdf:type rdf:resource="&swrl;AtomList"/>
<rdf:first>
<rdf:Description>
<rdf:type rdf:resource="&swrl;ClassAtom"/>
<swrl:classPredicate rdf:resource="&foaf;Person"/>
<swrl:argument1 rdf:resource="urn:swrl#p"/>
</rdf:Description>
</rdf:first>
<rdf:rest>
<rdf:Description>
<rdf:type rdf:resource="&swrl;AtomList"/>
<rdf:rest>
<rdf:Description>
<rdf:type rdf:resource="&swrl;AtomList"/>
<rdf:rest rdf:resource="&rdf;nil"/>
<rdf:first>
<rdf:Description>
<rdf:type rdf:resource="&swrl;BuiltinAtom"/>
<swrl:builtin rdf:resource="&swrlb;contains"/>
<swrl:arguments>
<rdf:Description>
<rdf:type rdf:resource="&rdf;List"/>
<rdf:first rdf:resource="urn:swrl#m"/>
<rdf:rest>
<rdf:Description>
<rdf:type rdf:resource="&rdf;List"/>
<rdf:first>@gmail.com</rdf:first>
<rdf:rest rdf:resource="&rdf;nil"/>
</rdf:Description>
</rdf:rest>
</rdf:Description>
</swrl:arguments>
</rdf:Description>
</rdf:first>
</rdf:Description>
</rdf:rest>
<rdf:first>
<rdf:Description>
<rdf:type rdf:resource="&swrl;DatavaluedPropertyAtom"/>
<swrl:propertyPredicate rdf:resource="http://www.jena.application.com/exploration#mbox"/>
<swrl:argument2 rdf:resource="urn:swrl#m"/>
<swrl:argument1 rdf:resource="urn:swrl#p"/>
</rdf:Description>
</rdf:first>
</rdf:Description>
</rdf:rest>
</rdf:Description>
</swrl:body>
<swrl:head>
<rdf:Description>
<rdf:type rdf:resource="&swrl;AtomList"/>
<rdf:rest rdf:resource="&rdf;nil"/>
<rdf:first>
<rdf:Description>
<rdf:type rdf:resource="&swrl;ClassAtom"/>
<swrl:classPredicate rdf:resource="http://www.jena.application.com/exploration#GmailPerson"/>
<swrl:argument1 rdf:resource="urn:swrl#p"/>
</rdf:Description>
</rdf:first>
</rdf:Description>
</swrl:head>
</rdf:Description>
</rdf:RDF>
<!-- Generated by the OWL API (version 3.4.2) http://owlapi.sourceforge.net -->
graph.owl - NoSQL精粹中文版封面图的RDF表示
<?xml version="1.0"?>
<!DOCTYPE rdf:RDF [
<!ENTITY graph "http://www.nosql.com/graph#" >
<!ENTITY owl "http://www.w3.org/2002/07/owl#" >
<!ENTITY xsd "http://www.w3.org/2001/XMLSchema#" >
<!ENTITY rdfs "http://www.w3.org/2000/01/rdf-schema#" >
<!ENTITY rdf "http://www.w3.org/1999/02/22-rdf-syntax-ns#" >
]>
<rdf:RDF xmlns="http://www.nosql.com/graph#"
xml:base="http://www.nosql.com/graph"
xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#"
xmlns:graph="http://www.nosql.com/graph#"
xmlns:owl="http://www.w3.org/2002/07/owl#"
xmlns:xsd="http://www.w3.org/2001/XMLSchema#"
xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
<owl:Ontology rdf:about="http://www.nosql.com/graph">
<owl:versionIRI rdf:resource="http://www.nosql.com/graph/1.0"/>
</owl:Ontology>
<!--
///////////////////////////////////////////////////////////////////////////////////////
//
// Object Properties
//
///////////////////////////////////////////////////////////////////////////////////////
-->
<!-- http://www.nosql.com/graph#author -->
<owl:ObjectProperty rdf:about="&graph;author">
<rdfs:domain rdf:resource="&graph;Book"/>
<rdfs:range rdf:resource="&graph;Person"/>
</owl:ObjectProperty>
<!-- http://www.nosql.com/graph#category -->
<owl:ObjectProperty rdf:about="&graph;category">
<rdfs:domain rdf:resource="&graph;Book"/>
<rdfs:range rdf:resource="&graph;BookCategory"/>
</owl:ObjectProperty>
<!-- http://www.nosql.com/graph#employee -->
<owl:ObjectProperty rdf:about="&graph;employee">
<rdfs:range rdf:resource="&graph;Company"/>
<rdfs:domain rdf:resource="&graph;Person"/>
</owl:ObjectProperty>
<!-- http://www.nosql.com/graph#friend -->
<owl:ObjectProperty rdf:about="&graph;friend">
<rdf:type rdf:resource="&owl;SymmetricProperty"/>
<rdfs:domain rdf:resource="&graph;Person"/>
<rdfs:range rdf:resource="&graph;Person"/>
</owl:ObjectProperty>
<!-- http://www.nosql.com/graph#like -->
<owl:ObjectProperty rdf:about="&graph;like">
<rdfs:range rdf:resource="&graph;Book"/>
<rdfs:domain rdf:resource="&graph;Person"/>
</owl:ObjectProperty>
<!--
///////////////////////////////////////////////////////////////////////////////////////
//
// Classes
//
///////////////////////////////////////////////////////////////////////////////////////
-->
<!-- http://www.nosql.com/graph#Book -->
<owl:Class rdf:about="&graph;Book"/>
<!-- http://www.nosql.com/graph#BookCategory -->
<owl:Class rdf:about="&graph;BookCategory"/>
<!-- http://www.nosql.com/graph#Company -->
<owl:Class rdf:about="&graph;Company"/>
<!-- http://www.nosql.com/graph#Person -->
<owl:Class rdf:about="&graph;Person"/>
<!--
///////////////////////////////////////////////////////////////////////////////////////
//
// Individuals
//
///////////////////////////////////////////////////////////////////////////////////////
-->
<!-- http://www.nosql.com/graph#Anna -->
<owl:NamedIndividual rdf:about="&graph;Anna">
<rdf:type rdf:resource="&graph;Person"/>
<friend rdf:resource="&graph;Barbara"/>
<employee rdf:resource="&graph;BigCo"/>
<like rdf:resource="&graph;Refactoring"/>
</owl:NamedIndividual>
<!-- http://www.nosql.com/graph#Barbara -->
<owl:NamedIndividual rdf:about="&graph;Barbara">
<rdf:type rdf:resource="&graph;Person"/>
<employee rdf:resource="&graph;BigCo"/>
<friend rdf:resource="&graph;Carol"/>
<friend rdf:resource="&graph;Elizabeth"/>
<like rdf:resource="&graph;NoSQL_Distilled"/>
<like rdf:resource="&graph;Refactoring"/>
</owl:NamedIndividual>
<!-- http://www.nosql.com/graph#BigCo -->
<owl:NamedIndividual rdf:about="&graph;BigCo">
<rdf:type rdf:resource="&graph;Company"/>
</owl:NamedIndividual>
<!-- http://www.nosql.com/graph#Carol -->
<owl:NamedIndividual rdf:about="&graph;Carol">
<rdf:type rdf:resource="&graph;Person"/>
<employee rdf:resource="&graph;BigCo"/>
<friend rdf:resource="&graph;Dawn"/>
<like rdf:resource="&graph;NoSQL_Distilled"/>
</owl:NamedIndividual>
<!-- http://www.nosql.com/graph#Database_Refactoring -->
<owl:NamedIndividual rdf:about="&graph;Database_Refactoring">
<rdf:type rdf:resource="&graph;Book"/>
<category rdf:resource="&graph;Databases"/>
<author rdf:resource="&graph;Pramod"/>
</owl:NamedIndividual>
<!-- http://www.nosql.com/graph#Databases -->
<owl:NamedIndividual rdf:about="&graph;Databases">
<rdf:type rdf:resource="&graph;BookCategory"/>
</owl:NamedIndividual>
<!-- http://www.nosql.com/graph#Dawn -->
<owl:NamedIndividual rdf:about="&graph;Dawn">
<rdf:type rdf:resource="&graph;Person"/>
<friend rdf:resource="&graph;Jill"/>
<like rdf:resource="&graph;NoSQL_Distilled"/>
</owl:NamedIndividual>
<!-- http://www.nosql.com/graph#Elizabeth -->
<owl:NamedIndividual rdf:about="&graph;Elizabeth">
<rdf:type rdf:resource="&graph;Person"/>
<friend rdf:resource="&graph;Jill"/>
<like rdf:resource="&graph;NoSQL_Distilled"/>
</owl:NamedIndividual>
<!-- http://www.nosql.com/graph#Jill -->
<owl:NamedIndividual rdf:about="&graph;Jill">
<rdf:type rdf:resource="&graph;Person"/>
</owl:NamedIndividual>
<!-- http://www.nosql.com/graph#Martin -->
<owl:NamedIndividual rdf:about="&graph;Martin">
<rdf:type rdf:resource="&graph;Person"/>
<friend rdf:resource="&graph;Pramod"/>
</owl:NamedIndividual>
<!-- http://www.nosql.com/graph#NoSQL_Distilled -->
<owl:NamedIndividual rdf:about="&graph;NoSQL_Distilled">
<rdf:type rdf:resource="&graph;Book"/>
<category rdf:resource="&graph;Databases"/>
<author rdf:resource="&graph;Martin"/>
<author rdf:resource="&graph;Pramod"/>
</owl:NamedIndividual>
<!-- http://www.nosql.com/graph#Pramod -->
<owl:NamedIndividual rdf:about="&graph;Pramod">
<rdf:type rdf:resource="&graph;Person"/>
</owl:NamedIndividual>
<!-- http://www.nosql.com/graph#Refactoring -->
<owl:NamedIndividual rdf:about="&graph;Refactoring">
<rdf:type rdf:resource="&graph;Book"/>
<author rdf:resource="&graph;Martin"/>
</owl:NamedIndividual>
</rdf:RDF>
<!-- Generated by the OWL API (version 3.4.2) http://owlapi.sourceforge.net -->
2 创建Dataset、加载数据
参考了二进制发布包中的实例代码，首先在./Store/DB1目录下创建数据集，该数据集的默认模型加载exploration.owl中数据，已命名模型加载graph.owl，加载是在TDB事务中完成的。
package tdb.examples;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.util.Iterator;
import com.hp.hpl.jena.query.Dataset;
import com.hp.hpl.jena.query.ReadWrite;
import com.hp.hpl.jena.rdf.model.Model;
import com.hp.hpl.jena.rdf.model.ModelFactory;
import com.hp.hpl.jena.tdb.TDBFactory;
public class ExTDB1 {
public static void main(String... argv) throws FileNotFoundException {
// 如果目录为空，则创建TDB索引文件和节点表
// If a directory is empty, the TDB files for indexes and node table are created.
// Direct way: Make a TDB-back Jena model in the named directory.
String directory = "./Store/DB1";
// 使用TDBFactory创建TDB数据集
Dataset dataset = TDBFactory.createDataset(directory);
// ... do work ...
// 开始事务
dataset.begin(ReadWrite.WRITE);
Model model = ModelFactory.createDefaultModel();
String nosqlBase = "http://www.nosql.com/graph";
model.read(new FileInputStream("./rdf/nosql/graph.owl"), nosqlBase);
dataset.addNamedModel(nosqlBase, model);// 命名模型
dataset.commit();
dataset.begin(ReadWrite.WRITE);
String base = "http://www.jena.application.com/exploration";
Model model2 = dataset.getDefaultModel();// 默认模型
model2.read(new FileInputStream("./rdf/application/exploration.owl"), base);
dataset.commit();
dataset.begin(ReadWrite.READ);
System.out.println("list dataset's Model names:");
Iterator<String> nameIter = dataset.listNames();
while (nameIter.hasNext()) {
System.out.println(nameIter.next());
}
// Model model3 = dataset.getNamedModel(base);
Model model3 = dataset.getDefaultModel();
System.out.println(model3.getGraph().toString());
dataset.end();
// 关闭数据集
dataset.close();
}
}
生成数据集文件结构(各文件含义暂不清楚)：
3 查询数据
以SPARQL查询支持数据集中数据查询，下面的代码分别在数据集中的两个模型中执行查询
package tdb.examples;
import com.hp.hpl.jena.query.Dataset;
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.Model;
import com.hp.hpl.jena.tdb.TDBFactory;
public class ExTDB4 {
public static void main(String... argv) {
// Direct way: Make a TDB-back Jena model in the named directory.
String directory = "./Store/DB1";
Dataset dataset = TDBFactory.createDataset(directory);
// Potentially expensive query.
String sparqlQueryString = "SELECT (count(*) AS ?count) { ?s ?p ?o }";
// See http://incubator.apache.org/jena/documentation/query/app_api.html
// 使用QueryFactory创建SPARQL查询
Query query = QueryFactory.create(sparqlQueryString);
Model defaultModel = dataset.getDefaultModel();
String nosqlBase = "http://www.nosql.com/graph";
Model namedModel = dataset.getNamedModel(nosqlBase);
// query defaultModel
QueryExecution qexec = QueryExecutionFactory.create(query, defaultModel);
ResultSet results = qexec.execSelect();
ResultSetFormatter.out(results);
qexec.close();
// query namedModel
QueryExecution qexec2 = QueryExecutionFactory.create(query, namedModel);
ResultSet results2 = qexec2.execSelect();
ResultSetFormatter.out(results2);
qexec2.close();
dataset.close();
}
}
有关Jena ARQ (SPARQL)可以参见 https://jena.apache.org/documentation/query/index.html，在Protege中编辑SPARQL查询是极好的：
也可以参考下面的代码片段执行SPARQL SELECT查询，其中包括了基本模型和推理后模型中的查询
package arq;
import static util.Constants.BOUNDARY;
import static util.Constants.NEWLINE;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import com.hp.hpl.jena.ontology.OntModelSpec;
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.QuerySolution;
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.RDFNode;
import com.hp.hpl.jena.reasoner.Reasoner;
import com.hp.hpl.jena.reasoner.ReasonerRegistry;
/**
* <ul>
* <li>Author: zhoujg | Date: 2014-4-5 下午10:14:49</li>
* <li>Description: Jena ARQ演示</li>
* </ul>
*/
public class JenaARQMain {
static Model model = null;
static InfModel infModel = null;
static void loadModel() {
model = ModelFactory.createOntologyModel(OntModelSpec.OWL_DL_MEM);
String nosqlBase = "http://www.nosql.com/graph";
try {
model.read(new FileInputStream("./rdf/nosql/graph.owl"), nosqlBase);
} catch (FileNotFoundException e) {
e.printStackTrace();
}
Reasoner reasoner = ReasonerRegistry.getOWLReasoner();
reasoner = reasoner.bindSchema(model);// tbox
infModel = ModelFactory.createInfModel(reasoner, model);// abox
}
public static void main(String[] args) {
loadModel();
// single value - base model
// queryFriend(model, "Pramod");// Martin
// queryFriend(model, "Martin");// null
// single value - inferred model
// queryFriend(infModel, "Pramod");// Martin
// queryFriend(infModel, "Martin");// Pramod
// multiple value - base model
// queryFriend(model, "Jill");// Elizabeth Dawn
// multiple value - inferred model
// queryFriend(infModel, "Barbara");// Anna Elizabeth Carol
// format resultset
queryFriendFormattedResultset(infModel, "Barbara");
}
static void sparqlFormatedResult(Model model, String query, String valueLabel) {
Query q = QueryFactory.create(query);
QueryExecution qexec = QueryExecutionFactory.create(q, model);
System.out.println("Plan to run SPARQL query: ");
System.out.println(BOUNDARY);
System.out.println(query);
System.out.println(BOUNDARY);
ResultSet rs = qexec.execSelect();
ResultSetFormatter.out(System.out, rs);
// ResultSetFormatter.outputAsXML(rs);// XML格式
// ResultSetFormatter.outputAsJSON(rs);// JSON格式
qexec.close();
}
static void sparql(Model model, String query, String valueLabel) {
Query q = QueryFactory.create(query);
QueryExecution qexec = QueryExecutionFactory.create(q, model);
System.out.println("Plan to run SPARQL query: ");
System.out.println(BOUNDARY);
System.out.println(query);
System.out.println(BOUNDARY);
ResultSet rs = qexec.execSelect();
while (rs.hasNext()) {
QuerySolution qs = rs.nextSolution();
RDFNode name = qs.get(valueLabel);
if (name != null) {
System.out.println("Found friend " + name.toString());
} else {
System.out.println("No friend found!");
}
}
qexec.close();
}
static void queryFriend(Model model, String name) {
StringBuilder sb = generateSPARQLPREFIX();
sb.append("SELECT DISTINCT ?friend WHERE { ?friend nosql:friend nosql:").append(name).append(" }").append(NEWLINE);
sparql(model, sb.toString(), "?friend");
}
static void queryFriendFormattedResultset(Model model, String name) {
StringBuilder sb = generateSPARQLPREFIX();
sb.append("SELECT DISTINCT ?friend WHERE { ?friend nosql:friend nosql:").append(name).append(" }").append(NEWLINE);
sparqlFormatedResult(model, sb.toString(), "?friend");
}
static StringBuilder generateSPARQLPREFIX() {
StringBuilder sb = new StringBuilder();
sb.append("PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>").append(NEWLINE).append("PREFIX owl: <http://www.w3.org/2002/07/owl#>")
.append(NEWLINE).append("PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>").append(NEWLINE)
.append("PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>").append(NEWLINE).append("PREFIX foaf: <http://xmlns.com/foaf/0.1/>")
.append(NEWLINE).append("PREFIX myfoaf: <http://blog.sina.com.cn/zhoujiagenontology/helloworld.owl#>").append(NEWLINE)
.append("PREFIX nosql: <http://www.nosql.com/graph#>").append(NEWLINE);
return sb;
}
}
4 遗留问题
能支持多大的存储数量级？ - SERIOUSLY, I am working on this. 2015/07/01 updated
影响查询时间的因素有哪些？
数据集中文件有什么含义？
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