[Rdfapi-php-interest] writing class instance as RDF

[AJ C. <ca...@gm...>]

I created a ResModel for an instance of class Experiment (from my own
ontology called "exp") and wrote it into RDF file using
$model->saveAs($save_file). In the RDF file, the class instance started with

<rdf:Description rdf:ID="i">

How do I tell the resmodel that it's an instance of Experiment class? I want
to have the RDF writen as
<rdf:RDF
    <exp:Experiment rdf:ID="i">
    ...

Thanks,
AJ