binarytableresultconstants.java

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/*  Sesame - Storage and Querying architecture for RDF and RDF Schema
 *  Copyright (C) 2001-2005 Aduna
 *
 *  Contact: 
 *  	Aduna
 *  	Prinses Julianaplein 14 b
 *  	3817 CS Amersfoort
 *  	The Netherlands
 *  	tel. [phone]
 *  	fax. [phone]
 *
 *  	http://aduna.biz/
 *  	http://www.openrdf.org/
 *  
 *  This library is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU Lesser General Public
 *  License as published by the Free Software Foundation; either
 *  version 2.1 of the License, or (at your option) any later version.
 *
 *  This library is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *  Lesser General Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public
 *  License along with this library; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
package org.openrdf.sesame.query;

/**
 * Interface defining constants for the binary table result format. Files in
 * this format consist of a header followed by zero or more records. Data fields
 * are encoded as specified in the interfaces <tt>java.io.DataInput</tt> and
 * <tt>java.io.DataOutput</tt>. The header is 12 bytes long:
 * <ul>
 * <li>Bytes 0-3 contain the ASCII codes for the string "BRTR", which stands for
 * Binary RDF Table Result.
 * <li>Bytes 4-7 specify the format version (an integer).
 * <li>Bytes 8-11 specify the number of columns of the query result that will
 * follow (an integer).
 * </ul>
 * Following this are the column headers, which are encoded as UTF-8 strings.
 * There are as many column headers as the number of columns that has been
 * specified in the header.
 * <p>
 * Zero or more records follow after the column headers. This can be a mixture
 * of records describing a result and supporting records. The results table is
 * described by the result records which are writtin from left to right, from
 * top to bottom. Each record starts with a record type marker (a single byte).
 * The following records are defined in the current format:
 *
 * <ul>
 * <li><tt>NULL</tt> (byte value: 0):<br>
 * This indicates a NULL value in the table and consists of nothing more than
 * the record type marker.
 *
 * <li><tt>REPEAT</tt> (byte value: 1):<br>
 * This indicates that the next value is identical to the value in the same
 * column in the previous row. The REPEAT record consists of nothing more than
 * the record type marker.
 *
 * <li><tt>NAMESPACE</tt> (byte value: 2):<br>
 * This is a supporting record that assigns an ID (non-negative integer) to a
 * namespace. This ID can later be used in in a QNAME record to combine it with
 * a local name to form a full URI. The record type marker is followed by a
 * non-negative integer for the ID and an UTF-8 encoded string for the
 * namespace.
 *
 * <li><tt>QNAME </tt>(byte value: 3):<br>
 * This indicates a URI value, the value of which is encoded as a namespace ID
 * and a local name. The namespace ID is required to be mapped to a namespace is
 * a previous NAMESPACE record. The record type marker is followed by a
 * non-negative integer (the namespace ID) and an UTF-8 encoded string for the
 * local name.
 *
 * <li><tt>URI</tt> (byte value: 4):<br>
 * This also indicates a URI value, but one that does not use a namespace ID.
 * This record type marker is simply followed by an UTF-8 encoded string for the
 * full URI.
 *
 * <li><tt>BNODE</tt> (byte value: 5):<br>
 * This indicates a blank node. The record type marker is followed by an UTF-8
 * encoded string for the bnode ID.
 *
 * <li><tt>PLAIN_LITERAL</tt> (byte value: 6):<br>
 * This indicates a plain literal value. The record type marker is followed by
 * an UTF-8 encoded string for the literal's label.
 *
 * <li><tt>LANG_LITERAL</tt> (byte value: 7):<br>
 * This indicates a literal value with a language attribute. The record type
 * marker is followed by an UTF-8 encoded string for the literal's label,
 * followed by an UTF-8 encoded string for the language attribute.
 *
 * <li><tt>DATATYPE_LITERAL</tt> (byte value: 8):<br>
 * This indicates a datatyped literal. The record type marker is followed by an
 * UTF-8 encoded string for the literal's label. Following this label is either
 * a QNAME or URI record for the literal's datatype.
 *
 * <li><tt>ERROR</tt> (byte value: 126):<br>
 * This record indicates a error. The type of error is indicates by the byte
 * directly following the record type marker: <tt>1</tt> for a malformed query
* error, <tt>2</tt> for a query evaluation error. The error type byte is
* followed by an UTF-8 string for the error message.
 *
 * <li><tt>TABLE_END</tt> (byte value: 127):<br>
 * This is a special record that indicates the end of the results table and
 * consists of nothing more than the record type marker. Any data following this
 * record should be ignored.
 * </ul>
 *
 * @author Arjohn Kampman
 * @version $Revision: 1.3 $
 */
public interface BinaryTableResultConstants {

	/** Magic number for Binary RDF Table Result files. **/
	public static final byte[] MAGIC_NUMBER = new byte[] {'B','R', 'T', 'R'};

	/** The version number of the current format. **/
	public static final int FORMAT_VERSION = 1;

	/* RECORD TYPES */
	public static final int NULL_RECORD_MARKER             = 0;
	public static final int REPEAT_RECORD_MARKER           = 1;
	public static final int NAMESPACE_RECORD_MARKER        = 2;
	public static final int QNAME_RECORD_MARKER            = 3;
	public static final int URI_RECORD_MARKER              = 4;
	public static final int BNODE_RECORD_MARKER            = 5;
	public static final int PLAIN_LITERAL_RECORD_MARKER    = 6;
	public static final int LANG_LITERAL_RECORD_MARKER     = 7;
	public static final int DATATYPE_LITERAL_RECORD_MARKER = 8;

	public static final int ERROR_RECORD_MARKER            = 126;
	public static final int TABLE_END_RECORD_MARKER        = 127;

	/* ERROR TYPES */
	public static final int MALFORMED_QUERY_ERROR  = 1;
	public static final int QUERY_EVALUATION_ERROR = 2;
}