/**
* 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" . $xml . "\n</rdf:RDF>\n";
}
protected function expandCurie($node, &$context, $value)
{
if (preg_match('/^(\\w*?):(.*)$/', $value, $matches)) {
list(, $prefix, $local) = $matches;
$prefix = strtolower($prefix);
if ($prefix === '_') {
// It is a bnode
return $this->remapBnode(substr($value, 2));
} elseif (empty($prefix) and $context['vocab']) {
// Empty prefix
return $context['vocab'] . $local;
} elseif (isset($context['prefixes'][$prefix])) {
return $context['prefixes'][$prefix] . $local;
} elseif ($uri = $node->lookupNamespaceURI($prefix)) {
return $uri . $local;
} elseif (!empty($prefix) and $uri = RdfNamespace::get($prefix)) {
// Expand using well-known prefixes
return $uri . $local;
}
}
}
/**
* Parses qnames and boolean values, which have equivalent starting
* characters.
* @ignore
*/
protected function parseQNameOrBoolean()
{
// First character should be a ':' or a letter
$c = $this->read();
if ($c == -1) {
throw new Exception("Turtle Parse Error: unexpected end of file while readying value", $this->line, $this->column);
}
if ($c != ':' && !self::isPrefixStartChar($c)) {
throw new Exception("Turtle Parse Error: expected a ':' or a letter, found '{$c}'", $this->line, $this->column);
}
$namespace = null;
if ($c == ':') {
// qname using default namespace
if (isset($this->namespaces[''])) {
$namespace = $this->namespaces[''];
} else {
throw new Exception("Turtle Parse Error: default namespace used but not defined", $this->line, $this->column);
}
} else {
// $c is the first letter of the prefix
$prefix = $c;
$c = $this->read();
while (self::isPrefixChar($c)) {
$prefix .= $c;
$c = $this->read();
}
if ($c != ':') {
// prefix may actually be a boolean value
$value = $prefix;
if ($value == "true" || $value == "false") {
return array('type' => 'literal', 'value' => $value, 'datatype' => RdfNamespace::get('xsd') . 'boolean');
}
}
$this->verifyCharacterOrFail($c, ":");
if (isset($this->namespaces[$prefix])) {
$namespace = $this->namespaces[$prefix];
} else {
throw new Exception("Turtle Parse Error: namespace prefix '{$prefix}' used but not defined", $this->line, $this->column);
}
}
// $c == ':', read optional local name
$localName = '';
$c = $this->read();
if (self::isNameStartChar($c)) {
if ($c == '\\') {
$localName .= $this->readLocalEscapedChar();
} else {
$localName .= $c;
}
$c = $this->read();
while (self::isNameChar($c)) {
if ($c == '\\') {
$localName .= $this->readLocalEscapedChar();
} else {
$localName .= $c;
}
$c = $this->read();
}
}
// Unread last character
$this->unread($c);
// Note: namespace has already been resolved
return array('type' => 'uri', 'value' => $namespace . $localName);
}
/**
* @ignore
*/
protected function serialisePrefixes()
{
$turtle = '';
foreach ($this->prefixes as $prefix => $count) {
$url = RdfNamespace::get($prefix);
$turtle .= "@prefix {$prefix}: <{$url}> .\n";
}
return $turtle;
}
/**
* @param $prefix
*
* @return string
*/
public function get($prefix)
{
return RdfNamespace::get($prefix);
}
