/**
* Method to serialise an EasyRdf\Graph to RDF/PHP
*
* http://n2.talis.com/wiki/RDF_PHP_Specification
* docs/appendix-a-rdf-formats-php.md
*
* @param Graph $graph An EasyRdf\Graph object.
* @param string $format The name of the format to convert to.
* @param array $options
*
* @throws Exception
* @return string The RDF in the new desired format.
*/
public function serialise($graph, $format, array $options = array())
{
parent::checkSerialiseParams($graph, $format);
if ($format != 'php') {
throw new Exception(__CLASS__ . " does not support: {$format}");
}
// Graph is already stored as RDF/PHP resource-centric array internally within the EasyRdf\Graph object
return $graph->toRdfPhp();
}
/**
* Method to serialise an EasyRdf\Graph to RDF/XML
*
* @param Graph $graph An EasyRdf\Graph object.
* @param string $format The name of the format to convert to.
* @param array $options
*
* @return string The RDF in the new desired format.
* @throws Exception
*/
public function serialise(Graph $graph, $format, array $options = array())
{
parent::checkSerialiseParams($format);
if ($format != 'rdfxml') {
throw new Exception("EasyRdf\\Serialiser\\RdfXml does not support: {$format}");
}
// store of namespaces to be appended to the rdf:RDF tag
$this->prefixes = array('rdf' => true);
// store of the resource URIs we have serialised
$this->outputtedResources = array();
$xml = '';
// Serialise URIs first
foreach ($graph->resources() as $resource) {
if (!$resource->isBnode()) {
$xml .= $this->rdfxmlResource($resource, true);
}
}
// Serialise bnodes afterwards
foreach ($graph->resources() as $resource) {
if ($resource->isBnode()) {
$xml .= $this->rdfxmlResource($resource, true);
}
}
// iterate through namepsaces array prefix and output a string.
$namespaceStr = '';
foreach ($this->prefixes as $prefix => $count) {
$url = RdfNamespace::get($prefix);
if (strlen($namespaceStr)) {
$namespaceStr .= "\n ";
}
if (strlen($prefix) === 0) {
$namespaceStr .= ' xmlns="' . htmlspecialchars($url) . '"';
} else {
$namespaceStr .= ' xmlns:' . $prefix . '="' . htmlspecialchars($url) . '"';
}
}
return "<?xml version=\"1.0\" encoding=\"utf-8\" ?>\n" . "<rdf:RDF" . $namespaceStr . ">\n" . $xml . "\n</rdf:RDF>\n";
}
/**
* Serialise an EasyRdf\Graph into N-Triples
*
* @param Graph $graph An EasyRdf\Graph object.
* @param string $format The name of the format to convert to.
* @param array $options
*
* @throws Exception
*
* @return string The RDF in the new desired format.
*/
public function serialise($graph, $format, array $options = array())
{
parent::checkSerialiseParams($graph, $format);
if ($format == 'ntriples') {
$nt = '';
foreach ($graph->toRdfPhp() as $resource => $properties) {
foreach ($properties as $property => $values) {
foreach ($values as $value) {
$nt .= $this->serialiseResource($resource) . " ";
$nt .= "<" . $this->escapeString($property) . "> ";
$nt .= $this->serialiseValue($value) . " .\n";
}
}
}
return $nt;
} else {
throw new Exception(__CLASS__ . " does not support: {$format}");
}
}
/**
* @param \EasyRdf\Graph $graph
* @param string $format
* @param array $options
*
* @throws Exception
* @return string
*/
public function serialise($graph, $format, array $options = array())
{
parent::checkSerialiseParams($graph, $format);
if ($format != 'jsonld') {
throw new Exception(__CLASS__ . ' does not support: ' . $format);
}
$ld_graph = new LD\Graph();
$nodes = array();
// cache for id-to-node association
foreach ($graph->toRdfPhp() as $resource => $properties) {
if (array_key_exists($resource, $nodes)) {
$node = $nodes[$resource];
} else {
$node = $ld_graph->createNode($resource);
$nodes[$resource] = $node;
}
foreach ($properties as $property => $values) {
foreach ($values as $value) {
if ($value['type'] == 'bnode' or $value['type'] == 'uri') {
if (array_key_exists($value['value'], $nodes)) {
$_value = $nodes[$value['value']];
} else {
$_value = $ld_graph->createNode($value['value']);
$nodes[$value['value']] = $_value;
}
} elseif ($value['type'] == 'literal') {
if (isset($value['lang'])) {
$_value = new LD\LanguageTaggedString($value['value'], $value['lang']);
} elseif (isset($value['datatype'])) {
$_value = new LD\TypedValue($value['value'], $value['datatype']);
} else {
$_value = $value['value'];
}
} else {
throw new Exception("Unable to serialise object to JSON-LD: " . $value['type']);
}
if ($property == "http://www.w3.org/1999/02/22-rdf-syntax-ns#type") {
$node->addType($_value);
} else {
$node->addPropertyValue($property, $_value);
}
}
}
}
// OPTIONS
$use_native_types = !(isset($options['expand_native_types']) and $options['expand_native_types'] == true);
$should_compact = (isset($options['compact']) and $options['compact'] == true);
$should_frame = isset($options['frame']);
// expanded form
$data = $ld_graph->toJsonLd($use_native_types);
if ($should_frame) {
$data = LD\JsonLD::frame($data, $options['frame'], $options);
}
if ($should_compact) {
// compact form
$compact_context = isset($options['context']) ? $options['context'] : null;
$compact_options = array('useNativeTypes' => $use_native_types, 'base' => $graph->getUri());
$data = LD\JsonLD::compact($data, $compact_context, $compact_options);
}
return LD\JsonLD::toString($data);
}
/**
* Serialise an EasyRdf\Graph to Turtle.
*
* @param Graph $graph An EasyRdf\Graph object.
* @param string $format The name of the format to convert to.
* @param array $options
*
* @return string The RDF in the new desired format.
* @throws Exception
*/
public function serialise(Graph $graph, $format, array $options = array())
{
parent::checkSerialiseParams($format);
if ($format != 'turtle' and $format != 'n3') {
throw new Exception("EasyRdf\\Serialiser\\Turtle does not support: {$format}");
}
$this->prefixes = array();
$this->outputtedBnodes = array();
$turtle = '';
$turtle .= $this->serialiseSubjects($graph, 'uri');
$turtle .= $this->serialiseSubjects($graph, 'bnode');
if (count($this->prefixes)) {
return $this->serialisePrefixes() . "\n" . $turtle;
} else {
return $turtle;
}
}
/**
* Serialise an EasyRdf\Graph into a GraphViz dot document.
*
* Supported output format names: dot, gif, png, svg
*
* @param Graph $graph An EasyRdf\Graph object.
* @param string $format The name of the format to convert to.
* @param array $options
*
* @return string The RDF in the new desired format.
* @throws Exception
*/
public function serialise(Graph $graph, $format, array $options = array())
{
parent::checkSerialiseParams($format);
switch ($format) {
case 'dot':
return $this->serialiseDot($graph);
case 'png':
case 'gif':
case 'svg':
return $this->renderImage($graph, $format);
default:
throw new Exception("EasyRdf\\Serialiser\\GraphViz does not support: {$format}");
}
}
