def in_general_ns(uri):
    """Return True iff the URI is in a well-known general RDF namespace.

    URI namespaces considered well-known are RDF, RDFS, OWL, SKOS and DC."""
    RDFuri = RDF.uri
    RDFSuri = RDFS.uri

    for ns in (RDFuri, RDFSuri, OWL, SKOS, DC):
        if uri.startswith(ns):
            return True
    return False