statement.java

Jena推理机

/*
	(c) Copyright 2000-2004, 2005, 2006, 2007 Hewlett-Packard Development Company, LP
	[See end of file]
	$Id: Statement.java,v 1.15 2007/01/02 11:48:35 andy_seaborne Exp $
*/


package com.hp.hpl.jena.rdf.model;

import com.hp.hpl.jena.graph.*;

/** An RDF Statement.
 *
 * <p>A Statement is not a Resource, but can produce a ReifiedStatement
 * that represents it and from which the Statement can be recovered.</p>
 *
 * <p>A statement instance tracks which model created it, if any. All the
 * Resource components of a Statement are in the same model as the
 * Statement, if it has one, and are in no model if the Statement isn't.</p>
 *
 * <p>This interface provides methods supporting typed literals.  This means
 *    that methods are provided which will translate a built in type, or an
 *    object to an RDF Literal.  This translation is done by invoking the
 *    <CODE>toString()</CODE> method of the object, or its built in equivalent.
 *    The reverse translation is also supported.  This is built in for built
 *    in types.  Factory objects, provided by the application, are used
 *    for application objects.</p>
 
 * @author bwm; additions by kers
 * @version $Name:  $ $Revision: 1.15 $ $Date: 2007/01/02 11:48:35 $
 */

public interface Statement extends FrontsTriple
{
    
    /** determine whether two statements are equal.
     *
     * <p> Two statements are considered to be equal if they have the
     *    the same subject, predicate and object.  A statement can
     *    only be equal to another statement object.
     * </p>
     * @return true if and only if the equality condition is met.
     * @param o the object to be compared
     */
    
    public boolean equals(Object o);
    
    /** Returns asTriple().hashCode()
     */
    public int hashCode();
    
    /** An accessor method to return the subject of the statements.
     * @return The subject of the statement.
     */
    public Resource getSubject();
    
    /** An accessor function to return the predicate of the statement.
     * @return The predicate of the statement.
     */
    public Property getPredicate();
    
    /** An accessor funtion to return the object of the statement.
     * @return Return the object of the statement.
     */
    public RDFNode getObject();
    
    /** Get a property of the object of the statement.
     *
     * <p>There is an unfortunate ambiguity here.  GetProperty would normally
     *  treat the statement as a resource, and return a property about this
     *  statement.  This is not what is wanted in most cases, so getProperty
     *  on a statement is defined to call getProperty on its object.  If
     *  a property of the statement itself is required, getStatementProperty
     *  should be used.</p>
     *
     * <p>If the object of the statement is not a resource, an exception is
     *  thrown.</p>
     * @param p the property sought
     
     * @return a statement representing an instance of the required
     * property
     */
    public Statement getProperty(Property p) ;
    
    /** Return a property of this statement.
     *
     * <p>The model associated with this statement is searched for a statement with
     *   this statement as subject and the specified property as predicate.  If
     *   such a statement is found it is return.  If more than one exists in the
     *   model, then it is undefined which is returned.  If no such statement
     *   exists, an exception is thrown.</p>
     * @param p the property sought
     
     * @return a statement representing an instance of the specified
     * property.
     */
    public Statement getStatementProperty(Property p) ;
    
    /** Return the object of the statement.
     *
     * <p>An exception will be thrown if the object is not a resource.</p>
     * 
     * @return The Resource which is the object of the statement.
     */
    public Resource getResource() ;
    
    /** Return the object of the statement.
     *
     * <p>An exception will be thrown if the object is not a Literal.</p>
     * 
     * @return The Literal which is the object of the statement.
     */
    public Literal getLiteral() ;
    
    /** Return the object of the statement.
     *
     * <p>An exception will be thrown if the object is not a Literal.</p>
     * 
     * @return The object of the statement interpreted as a value of the
     * the specified type.
     */    
    public boolean getBoolean() ;
    
    /** Return the object of the statement.
     *
     * <p>An exception will be thrown if the object is not a Literal.</p>
     * 
     * @return The object of the statement interpreted as a value of the
     * the specified type.
     */    
    public byte getByte() ;
    
    /** Return the object of the statement.
     *
     * <p>An exception will be thrown if the object is not a Literal.</p>
     * 
     * @return The object of the statement interpreted as a value of the
     * the specified type.
     */    
    public short getShort() ;
    
    /** Return the object of the statement.
     *
     * <p>An exception will be thrown if the object is not a Literal.</p>
     * 
     * @return The object of the statement interpreted as a value of the
     * the specified type.
     */    
    public int getInt() ;
    
    /** Return the object of the statement.
     *
     * <p>An exception will be thrown iof the object is not a Literal.</p>
     * 
     * @return The object of the statement interpreted as a value of the
     * the specified type.
     */    
    public long getLong() ;
    
    /** Return the object of the statement.
     *
     * <p>An exception will be thrown if the object is not a Literal.</p>
     * 
     * @return The object of the statement interpreted as a value of the
     * the specified type.
     */    
    public char getChar() ;
    
    /** Return the object of the statement.
     *
     * <p>An exception will be thrown if the object is not a Literal.</p>
     * 
     * @return The object of the statement interpreted as a value of the
     * the specified type.
     */    
    public float getFloat() ;
    
    /** Return the object of the statement.
     *
     * <p>An exception will be thrown if the object is not a Literal.</p>
     * 
     * @return The object of the statement interpreted as a value of the
     * the specified type.
     */    
    public double getDouble() ;
    
    /** Return the object of the statement.
     *
     * <p>An exception will be thrown if the object is not a Literal.</p>
     * 
     * @return The object of the statement interpreted as a value of the
     * the specified type.
     */ 
    public String getString() ;
    
    /** Return the object of the statement.
     *
     * <p>An exception will be thrown if the object is not a Resource.</p>
     * @return The object of the statement.
     * 
     */    
    public Resource getResource(ResourceF f) ;
    
    /** Return the object of the statement.
     * <p>An exception will be thrown if the object is not a Literal.</p>
     * @return The object of the statement.
     * @param f A factory used to create the returned object.
     * 
     */    
    public Object getObject(ObjectF f) ;
    
    /** Return the object of the statement.
     *
     * <p>An exception will be thrown if the object is not a Resource.</p>
     * 
     * @return The object of the statement interpreted as a value of the
     * the specified type.
     */    
    public Bag getBag() ;