http://stardog.com/docs/using/#export shows help for exporting a db into "ttl" file.
I wanted to export the database into some common formats like "rdf" or "owl".
How to export to OWL format or RDF format?
The following command should do the job (export in RDF/XML, classical RDF):
$ stardog export -c myDatabase --format RDFXML myDatabase_output.rdf