TupleDType dtype = new TupleDType();
dtype.addElement("a", new SimpleDType("http://bla"));
dtype.addElement("b", new SimpleDType("http://blabla"));
dtype.addElement("c", simpleDType);
CollectionDType collectionDType = new CollectionDType(simpleDType, "Set");
registry.registerDType(dTypeName, collectionDType);
}