+<!DOCTYPE rdf:RDF [
+ <!ENTITY rdfns 'http://www.w3.org/1999/02/22-rdf-syntax-ns#'>
+ <!ENTITY hthns 'http://www.cs.unibo.it/helm/schemas/schema-helmth#'>
+ <!ENTITY hns 'http://www.cs.unibo.it/helm/schemas/schema-helm#'>
+
+ ]>
+<rdf:RDF xml:lang="en" xmlns:rdf="&rdfns;" xmlns:h="&hns;" xmlns:hth="&hthns;">