public function readData($source_definition, $rest_parameters = array())
{
// Fetch the URI of the rdf file
$uri = $source_definition['uri'];
$format = strtolower($source_definition['format']);
$content = file_get_contents($uri);
// Try parsing the contents of the rdf file
$graph = new Graph();
$parser;
if ($format == 'turtle') {
$parser = new Turtle();
} elseif ($format == 'xml') {
// EasyRdf identifies rdfxml with rdf, not with xml as a format
$format = 'rdfxml';
$parser = new RdfXml();
} else {
\App::abort(500, "The format you added, {$format}, is not supported. The supported formats are turtle and xml.");
}
$triples_added = $parser->parse($graph, $content, $format, '');
$data = new Data();
$data->data = $graph;
$data->is_semantic = true;
$data->preferred_formats = $this->getPreferredFormats();
return $data;
}
protected function open()
{
// Perform XLST
$xsl_url = "https://webgate.ec.europa.eu/CITnet/stash/projects/ODCKAN/repos/iso-19139-to-dcat-ap/browse/iso-19139-to-dcat-ap.xsl?raw";
$proc = null;
try {
$xml = new DOMDocument();
$xml->load($this->extractor->uri);
$xsl = new DOMDocument();
$xsl->load($xsl_url);
$proc = new XSLTProcessor();
$proc->importStyleSheet($xsl);
} catch (\ErrorException $ex) {
$this->log('Something went wrong: ' . $ex->getMessage());
die;
}
$dcat_document = $proc->transformToXML($xml);
\EasyRdf\RdfNamespace::set('locn', 'http://www.w3.org/ns/locn#');
// Parse the dcat graph
$graph = new Graph();
$rdf_parser = new RdfXml();
$rdf_parser->parse($graph, $dcat_document, 'rdfxml', 'http://foo');
$this->datasets = $graph->allOfType('dcat:Dataset');
}
public function readData($source_definition, $rest_parameters = array())
{
$endpoint = $source_definition['endpoint'];
$endpoint_user = $source_definition['endpoint_user'];
$endpoint_password = $source_definition['endpoint_password'];
$query = $source_definition['query'];
$limitInQuery = false;
//Check if the query is already paged.
if (stripos($source_definition['query'], 'limit')) {
$limitInQuery = true;
} else {
list($limit, $offset) = Pager::calculateLimitAndOffset();
// Sparql endpoints often have a built in limit on the amount of rows that they return
// Avoid problems by capping the given limit by the Pager class
if ($limit > self::$MAX_LIMIT) {
$limit = self::$MAX_LIMIT;
}
}
// Retrieve the necessary variables to read from a SPARQL endpoint
$uri = \Request::url();
// Process the if and ifnot-statements in the query
$query = $this->processLogicalStatements($query);
// Process the parameters in the uri (to catch hashtag values for example)
$query = $this->processParameters($query);
// Create a count query for paging purposes, this assumes that a where clause is included in the query
// Note that the where "clause" is obligatory but it's not mandatory it is preceded by a WHERE keyword
$matches = array();
$keyword = "";
// If a select statement has been passed, we ask for JSON results
// If a construct statement has been passed, we ask for RDF/XML
// This piece of code can be removed in later versions as the query_type will be determined
// upon saving/editing a query
if (stripos($query, "select") !== false) {
// SELECT query
$keyword = "select";
} elseif (stripos($query, "construct") !== false) {
// CONSTRUCT query
$keyword = "construct";
} else {
// No valid SPARQL keyword has been found, is checked during validation
\App::abort(500, "No CONSTRUCT or SELECT statement has been found in the given query: {$query}");
}
// Prepare the count query for paging purposes
// This implies the removal of the select or construct statement
// and only using the where statement
// Make a distinction between select and construct since
// construct will be followed by a {} sequence, whereas a select statement will not
$prefix = '';
$filter = '';
// Covers FROM <...> FROM <...> WHERE{ } , FROM <...> FROM <...> { }, WHERE { }, { }
$where_clause = '(.+((FROM.*<.+>)+.*{.+})|((GRAPH.*<.+>)+.*{.+})|.*?(WHERE.*{.+})|.*?({.+}))[a-zA-Z0-9]*?';
$matches = array();
if ($keyword == 'select') {
$regex = $keyword . $where_clause;
preg_match_all("/(.*?){$regex}/msi", $query, $matches);
} else {
preg_match_all("/(.*?){$keyword}(\\s*\\{[^{]+\\}){$where_clause}/mis", $query, $matches);
}
$prefix = $matches[1][0];
$filter = "";
// Preg match all has 3 entries for the where clause, pick the first hit
if (!empty($matches[3][0])) {
$filter = $matches[3][0];
}
if (!empty($matches[4][0]) && empty($filter)) {
$filter = $matches[4][0];
}
if (!empty($matches[5][0]) && empty($filter)) {
$filter = $matches[5][0];
}
$last_element = end($matches);
if (!empty($last_element[0]) && empty($filter)) {
$filter = $last_element[0];
}
if (empty($filter)) {
\App::abort(500, "Failed to retrieve the where clause from the query: {$query}");
}
if (!$limitInQuery) {
// Prepare the query to count results
$count_query = $matches[1][0] . ' SELECT (count(*) AS ?count) ' . $filter;
$count_query = urlencode($count_query);
$count_query = str_replace("+", "%20", $count_query);
$count_uri = $endpoint . '?query=' . $count_query . '&format=' . urlencode("application/sparql-results+json");
$response = $this->executeUri($count_uri, $endpoint_user, $endpoint_password);
$response = json_decode($response);
// If something goes wrong, the resonse will either be null or false
if (!$response) {
\App::abort(500, "Something went wrong while executing the count query. The assembled URI was: {$count_uri}");
}
$count = $response->results->bindings[0]->count->value;
// Calculate page link headers, previous, next and last based on the count from the previous query
$paging = Pager::calculatePagingHeaders($limit, $offset, $count);
}
$query = $source_definition['query'];
$query = $this->processLogicalStatements($query);
$query = $this->processParameters($query);
if (!$limitInQuery) {
if (!empty($offset)) {
$query = $query . " OFFSET {$offset} ";
}
if (!empty($limit)) {
$query = $query . " LIMIT {$limit}";
}
}
// Prepare the query with proper encoding for the request
$query = str_replace('%23', '#', $query);
$q = urlencode($query);
$q = str_replace("+", "%20", $q);
if ($keyword == 'select') {
$query_uri = $endpoint . '?query=' . $q . '&format=' . urlencode("application/sparql-results+json");
$response = $this->executeUri($query_uri, $endpoint_user, $endpoint_password);
$result = json_decode($response, true);
if (!$result) {
\App::abort(500, 'The query has been executed, but the endpoint failed to return sparql results in JSON.');
}
$is_semantic = false;
} else {
$query_uri = $endpoint . '?query=' . $q . '&format=' . urlencode("application/rdf+xml");
$response = $this->executeUri($query_uri, $endpoint_user, $endpoint_password);
// Parse the triple response and retrieve the triples from them
$result = new Graph();
$parser = new RdfXml();
$parser->parse($result, $response, 'rdfxml', null);
$is_semantic = true;
}
// Create the data object to return
$data = new Data();
if (!$limitInQuery) {
$data->paging = $paging;
}
$data->data = $result;
$data->is_semantic = $is_semantic;
$data->preferred_formats = $this->getPreferredFormats();
if ($is_semantic) {
// Fetch the available namespaces and pass
// them as a configuration of the semantic data result
$ontologies = $this->ontologies->getAll();
$prefixes = array();
foreach ($ontologies as $ontology) {
$prefixes[$ontology["prefix"]] = $ontology["uri"];
}
$data->semantic = new \stdClass();
$data->semantic->conf = array('ns' => $prefixes);
$data->preferred_formats = array('ttl', 'jsonld', 'rdf');
}
// Determine which parameters were given in the query
$matches = array();
$query_parameters = array();
preg_match_all("/\\\$\\{(.+?)\\}/", $source_definition['query'], $matches);
if (!empty($matches[1])) {
$matches = $matches[1];
foreach ($matches as $entry) {
array_push($query_parameters, $entry);
}
}
$data->optional_parameters = $query_parameters;
return $data;
}
