Apache Jena is an open-source Java framework for building Semantic Web and Linked Data applications. It provides a comprehensive set of tools and libraries for working with RDF, SPARQL, and OWL, enabling developers to create, manipulate, and query semantic data models.

Pros

• Comprehensive toolkit for Semantic Web development
• Strong community support and regular updates
• Excellent documentation and extensive examples
• Supports various data storage options (in-memory, TDB, and database backends)

Cons

• Steep learning curve for newcomers to Semantic Web technologies
• Performance can be an issue with large datasets
• Limited support for non-Java programming languages

Code Examples

1. Creating and querying an RDF model:

Model model = ModelFactory.createDefaultModel();
model.read("data.ttl");

String queryString = "SELECT ?subject ?predicate ?object WHERE { ?subject ?predicate ?object }";
Query query = QueryFactory.create(queryString);
QueryExecution qexec = QueryExecutionFactory.create(query, model);
ResultSet results = qexec.execSelect();

while (results.hasNext()) {
    QuerySolution solution = results.nextSolution();
    System.out.println(solution);
}

2. Creating and writing an OWL ontology:

OntModel ontModel = ModelFactory.createOntologyModel(OntModelSpec.OWL_MEM);
String ns = "http://example.org/ontology#";

OntClass personClass = ontModel.createClass(ns + "Person");
OntClass employeeClass = ontModel.createClass(ns + "Employee");
employeeClass.addSuperClass(personClass);

ObjectProperty worksFor = ontModel.createObjectProperty(ns + "worksFor");
worksFor.addDomain(employeeClass);
worksFor.addRange(ontModel.createClass(ns + "Company"));

ontModel.write(System.out, "RDF/XML");

3. Performing SPARQL updates:

Dataset dataset = TDBFactory.createDataset("path/to/tdb");
String updateString = "PREFIX dc: <http://purl.org/dc/elements/1.1/> " +
                      "INSERT DATA { <http://example/book1> dc:title \"A new book\" ; dc:creator \"A.N.Author\" . }";

UpdateRequest update = UpdateFactory.create(updateString);
UpdateProcessor processor = UpdateExecutionFactory.create(update, dataset);
processor.execute();

Getting Started

To start using Apache Jena in your Java project, add the following dependencies to your Maven pom.xml file:

<dependencies>
    <dependency>
        <groupId>org.apache.jena</groupId>
        <artifactId>apache-jena-libs</artifactId>
        <version>4.6.1</version>
        <type>pom</type>
    </dependency>
</dependencies>

Then, you can create a simple RDF model and add a triple:

import org.apache.jena.rdf.model.*;

Model model = ModelFactory.createDefaultModel();
String ns = "http://example.org/";
Resource subject = model.createResource(ns + "subject");
Property predicate = model.createProperty(ns + "predicate");
RDFNode object = model.createLiteral("object");
model.add(subject, predicate, object);

model.write(System.out, "TURTLE");

This will create an RDF model, add a triple, and print it in Turtle format.