[Rdfapi-php-interest] serializing ontology

hi,

I have just started to use RAP - RDF API and facing some problem in
searlizing OntModel..my codes runs without error but nothing is
serialized...The output file contains only this

=========== contents of output file ==================
<rdf:RDF xmlns:rdf='http://www.w3.org/1999/02/22-rdf-syntax-ns#' />
==========================================

here is what I was trying


<?php
//================ my code ====================

$basename = *'http://www.findnwrite.com/courses/'*;

//Create OntModel

$ontModel = ModelFactory::getOntModel(MEMMODEL,RDFS_VOCABULARY, $basename);

// Add Classes and Properties

$clsDepartment = $ontModel->createOntClass($basename . "Department");

$clsCourses = $ontModel->createOntClass($basename . "Courses");

$prpRequires = $ontModel->createOntProperty($basename.*'requires'*);

$prpCredit = $ontModel->createOntProperty($basname.*'credit'*);

$prpStatisfy = $ontModel->createOntProperty($basename.*'statisfy'*);

$prpLabel = $ontModel->createOntProperty(RDFS::LABEL());

$prpSource = $ontModel->createOntProperty(DC::SOURCE());

$prpComment = $ontModel->createOntProperty(RDFS::COMMENT());

 //Create a subclass for department

$department = $courses[*'Department'*][*'name'*];

$dept = $courses[*'Department'*][*'sname'*];

//Save the model

$ontModel->saveAs($department . *'.owl'*, "rdf");
*

echo* "{$department}: " . $ontModel->size() . *'statements were added'*;
?>

I will be thankful if someone can tell me where I am making a mistake

Regards
ritesh

-- 
-------------------------------
http://findnwrite.com