rdf:datatype prefixes in XML serialization

[temcdrm]

Hi - I'm not sure if this is a bug or my lack of understanding. I'm trying to use prefixes in rdf:datatype attributes, and they appear in turtle serializations but not pretty-xml nor xml. Here is a code snippet:

import rdflib
import uuid

CIM_NS = 'http://www.ucaiug.org/profile#'

if __name__ == '__main__':
  g = rdflib.Graph()
  CIM = rdflib.Namespace (CIM_NS)
  g.bind('cim', CIM)

  ID = str(uuid.uuid4()).upper()
  ac = rdflib.URIRef (ID)
  g.add ((ac, rdflib.URIRef (CIM_NS + 'Equipment.inService'), rdflib.Literal (True, datatype='cim:Boolean')))
  g.add ((ac, rdflib.URIRef (CIM_NS + 'Conductor.length'), rdflib.Literal (1.0, datatype=CIM.Length)))
  g.add ((ac, rdflib.URIRef (CIM_NS + 'ACLineSegment.r'), rdflib.Literal (1.0)))

  g.serialize (destination='test1.xml', format='pretty-xml', max_depth=1)

Here is the XML output:

<?xml version="1.0" encoding="utf-8"?>
<rdf:RDF
  xmlns:cim="http://www.ucaiug.org/profile#"
  xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
>
  <rdf:Description rdf:about="00F9F912-4A31-423E-B649-67CD2157F9CA">
    <cim:Equipment.inService rdf:datatype="cim:Boolean">true</cim:Equipment.inService>
    <cim:Conductor.length rdf:datatype="http://www.ucaiug.org/profile#Length">1.0</cim:Conductor.length>
    <cim:ACLineSegment.r rdf:datatype="http://www.w3.org/2001/XMLSchema#double">1.0</cim:ACLineSegment.r>
  </rdf:Description>
</rdf:RDF>

The XML output doesn't apply a prefix to either CIM or XSD namespace, unless I hard-wire it.

[temcdrm]

Submitted an issue: 3321