iter = TripleIteratorFactory.defaultInstance().fromStream(relsDatastreamIS, RDFFormat.RDF_XML);
newIter = new FilteredTripleIterator(iter, toPurge, false);
ByteArrayOutputStream out = new ByteArrayOutputStream();
newIter.toStream(out, RDFFormat.RDF_XML, false);
if (newIter.wasChangeMade()) {
XMLDatastreamProcessor newdsxml = dsxml.newVersion();
Datastream newds = newdsxml.getDatastream();
// TODO: setting of this on DatastreamAsXML