Difference between revisions of "XDI4j Tutorial 1"

Revision as of 11:03, 16 December 2008

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Interfaces and classes

Graph

 org.eclipse.higgins.xdi4j.Graph;

This interface represents a whole XDI graph. XDI graphs consist of subjects, predicates, literals, references and inner graphs. Operations on the graph include creating these graph components, finding and manipulating them

Subject

 org.eclipse.higgins.xdi4j.Subject;

This interface represents a subject in an XDI graph. Methods include creating and finding predicates of the subject.

Predicate

 org.eclipse.higgins.xdi4j.Predicate;

This interface represents a predicate in an XDI graph. Methods include creating and finding references, literals and inner graphs of the predicate.

Reference

 org.eclipse.higgins.xdi4j.Reference;

This interface represents a reference in an XDI graph.

Literal

 org.eclipse.higgins.xdi4j.Literal;

This interface represents a literal in an XDI graph.

Statement

 org.eclipse.higgins.xdi4j.Statement;

This interface represents a statement in an XDI graph.

A statement consists of either:

• A subject (if the subject has no predicates).
• A subject and a predicate (if the predicate has no references or literals).
• A subject and a predicate and a reference.
• A subject and a predicate and a literal.
• A subject and a predicate and an inner graph.

A statement never has BOTH an reference and a literal.

GraphFactory

 org.eclipse.higgins.xdi4j.GraphFactory;

Graph factories exist for all implementations of the Graph interface (e.g. Memory, XML, Hibernate). They can be used to create a new XDI document, or to load an existing one.

Example

This example app shows how to create a new XDI document and how to perform basic graph operations on it.

package org.eclipse.higgins.xdi4j.tutorial;

import org.eclipse.higgins.xdi4j.Graph;
import org.eclipse.higgins.xdi4j.GraphFactory;
import org.eclipse.higgins.xdi4j.Predicate;
import org.eclipse.higgins.xdi4j.Subject;
import org.eclipse.higgins.xdi4j.impl.memory.MemoryGraphFactory;
import org.eclipse.higgins.xdi4j.xri3.impl.XRI3Segment;

/**
 * This example app shows how to create a new XDI
 * document and how to perform basic graph operations on it.
 * 
 * @author msabadello at parityinc dot not
 *
 */
public class Tutorial1 {

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

		GraphFactory factory = MemoryGraphFactory.getInstance();
		Graph graph = factory.openGraph();

		// there are basically two ways of working with graphs

		// 1) work with subjects, predicates, references and literals

		Subject markus = graph.createSubject(new XRI3Segment("=markus"));

		Predicate name = markus.createPredicate(new XRI3Segment("+name"));
		Predicate friend = markus.createPredicate(new XRI3Segment("+friend"));

		name.createLiteral("Markus");
		friend.createReference(new XRI3Segment("=drummond"));

		// 2) work with statements

		graph.createStatement(new XRI3Segment("=markus"), new XRI3Segment("+friend"), new XRI3Segment("=giovanni"));
		graph.createStatement(new XRI3Segment("=giovanni"), new XRI3Segment("+friend"), new XRI3Segment("=drummond"));

		// after our graph is filled, we can output it

		System.out.println(graph.toString());

		graph.close();
	}
}