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<?php
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// $Id$
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/**
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* sparql.client.inc - SPARQL HTTP client implementation.
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*
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* @author Arto Bendiken <http://bendiken.net/>
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* @copyright Copyright (c) 2007-2008 Arto Bendiken. All rights reserved.
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* @license GPL <http://creativecommons.org/licenses/GPL/2.0/>
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* @package sparql.module
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*/
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//////////////////////////////////////////////////////////////////////////////
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// SPARQL HTTP client
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function sparql_request($endpoint, $query, $options = array(), &$errors = NULL) {
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$options = array_merge(array('query' => $query, 'format' => 'application/sparql-results+json', 'output' => 'json'), $options);
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// HACK
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if (!isset($options['default-graph-uri']) && preg_match('!dbpedia!', $endpoint)) {
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$options['default-graph-uri'] = 'http://dbpedia.org';
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}
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$request = $endpoint . '?' . http_build_query($options, NULL, '&');
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$headers = array('Accept' => $options['format'] . ', */*');
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if ($response = drupal_http_request($request, $headers, 'GET')) {
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if (empty($response->code) && empty($response->data)) {
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$errors[] = t('Remote SPARQL query timed out; please try again.');
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}
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else if (isset($response->error) && empty($response->error)) {
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// This is seen when specifying a URL that doesn't even resolve
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$errors[] = t('Invalid SPARQL endpoint specified.');
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}
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else if (isset($response->error)) {
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$error = str_replace(SPARQL_Query::prefixes() . "\n", '', $response->data);
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$errors[] = t('Remote SPARQL endpoint returned error: %error', array('%error' => $error));
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}
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else if (preg_match('!^([\w]+/[^;]+)!', $response->headers['Content-Type'], $matches)) {
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switch ($format = $matches[1]) {
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case 'application/sparql-results+json':
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case 'application/json':
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case 'application/javascript':
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case 'text/javascript':
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return sparql_parse_json_results($response->data);
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case 'application/sparql-results+xml':
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case 'application/xml':
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case 'text/xml':
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case 'text/plain': // CIA Factbook returns this
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return sparql_parse_xml_results($response->data);
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default:
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foreach (rdf_get_formats('info', 'r') as $reader) {
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if ($reader->mime_type == $format) {
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if ($result = rdf_unserialize($response->data, array('format' => $reader->name, 'uri' => $endpoint)))
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return new ArrayIterator($result);
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break;
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}
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}
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$errors[] = t('Unknown SPARQL results format: %type.', array('%type' => $format));
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break;
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}
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}
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}
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return NULL;
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}
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/**
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* Parses query results in application/sparql-results+json format.
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*
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* @see http://www.w3.org/TR/rdf-sparql-json-res/
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*/
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function sparql_parse_json_results($input) {
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$input = json_decode($input);
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if (isset($input->boolean)) {
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return (bool)$input->boolean;
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}
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$output = $bnodes = array();
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foreach ($input->results->bindings as $row) {
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$item = array();
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foreach (get_object_vars($row) as $field => $binding) {
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switch ($binding->type) {
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case 'uri':
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$value = rdf_uriref($binding->value);
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break;
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case 'bnode':
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$bnode_id = $binding->value;
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$value = isset($bnodes[$bnode_id]) ? $bnodes[$bnode_id] : ($bnodes[$bnode_id] = rdf_bnode());
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break;
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case 'literal':
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$value = isset($binding->{'xml:lang'}) ? rdf_literal($binding->value, $binding->{'xml:lang'}) : $binding->value;
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break;
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case 'typed-literal':
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$value = rdf_literal($binding->value, NULL, rdf_uriref($binding->datatype));
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break;
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default: // unknown/invalid
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continue 2; // skip this binding
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break;
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}
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$item[$field] = $value;
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}
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$output[] = $item;
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}
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return $output;
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}
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/**
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* Parses query results in application/sparql-results+xml format.
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*
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* @see http://www.w3.org/TR/rdf-sparql-XMLres/
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*/
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function sparql_parse_xml_results($input) {
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// FIXME: we seem to have some encoding issues querying against DBpedia.
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$input = simplexml_load_string($input);
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if (isset($input->boolean)) {
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return (string)$input->boolean == 'true';
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}
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$output = $bnodes = array();
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foreach ($input->results->result as $result) {
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$item = array();
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foreach ($result->binding as $binding) {
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if (isset($binding->uri)) {
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$value = rdf_uriref((string)$binding->uri);
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}
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else if (isset($binding->bnode)) {
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$bnode_id = (string)$binding->bnode;
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$value = isset($bnodes[$bnode_id]) ? $bnodes[$bnode_id] : ($bnodes[$bnode_id] = rdf_bnode());
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}
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else {
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$literal = $binding->literal;
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$datatype = isset($literal['datatype']) ? rdf_uriref((string)$literal['datatype']) : NULL;
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$language = _sparql_parse_xml_results_language($literal);
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$value = rdf_literal((string)$literal, $language, $datatype);
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}
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$item[(string)$binding['name']] = $value;
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}
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$output[] = $item;
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}
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return $output;
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}
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function _sparql_parse_xml_results_language($element) {
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foreach ($element->attributes('http://www.w3.org/XML/1998/namespace') as $name => $value) {
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if ($name == 'lang') {
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return (string)$value;
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}
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}
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}
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