sub isRdfUri { # return true if the uri is an rdf uri, false otherwise
# typycal rdf uri:
# helm:rdf/cic:www.cs.unibo.it/helm/rdf/foo_schema//cic:\
sub isRdfUri { # return true if the uri is an rdf uri, false otherwise
# typycal rdf uri:
# helm:rdf/cic:www.cs.unibo.it/helm/rdf/foo_schema//cic:\