/**
* Checks if a new statement is already in the Model and adds the statement, if it is not in the Model.
* addWithoutDuplicates() is significantly slower then add().
* Retruns TRUE if the statement is added.
* FALSE otherwise.
* Expects a statements with ResResources(ResLiterals)
*
* @param object Statement $statement
* @return boolean
* @access public
* @throws PhpError
*/
function addWithoutDuplicates($statement)
{
return $this->model->addWithoutDuplicates(new Statement($this->_resNode2Node($statement->getSubject()), $this->_resNode2Node($statement->getPredicate()), $this->_resNode2Node($statement->getObject())));
}