/*
* Copyright Aduna (http://www.aduna-software.com/) (c) 1997-2007.
*
* Licensed under the Aduna BSD-style license.
*/
package org.openrdf.query.resultio.binary;
import java.io.DataInput;
import java.io.DataOutput;
/**
* 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 {@link DataInput} and
* {@link DataOutput}, except for the encoding of string values. String values
* are encoded in UTF-8 and are preceeded by a 32-bit integer specifying the
* length in bytes of this UTF-8 encoded string.
* <p>
* The file header is 13 bytes long:
* <ul>
* <li>Bytes 1-4 contain the ASCII codes for the string "BRTR", which stands
* for Binary RDF Table Result.
* <li>Bytes 5-8 specify the format version (an integer).
* <li>Byte 9 specifies some flags, specifically 'distinct' and 'ordered'.
* <li>Bytes 10-13 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 written 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 in
* 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
*/
public interface BinaryQueryResultConstants {
/**
* 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 = 3;
/* 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;
}