SYNTAX: http://www.w3.org/2000/03/rdf-tracking/#rdfms-empty-property-elements

I found these corner cases when updating the RDF/XML Syntax doc.
I've written them as test cases so we can precisely write down the
answer but the basic questions are (on an empty propertyElt):

  Is rdf:bagID allowed in these cases?
  If so, does rdf:bagID do anything when the bag is empty
  
At present, I've written it so that it is allowed and always
generates the N3
  <whatever> rdf:type rdf:Bag .
aka N-Triples:
  <whatever> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://www.w3.org/1999/02/22-rdf-syntax-ns#Bag> .

Dave

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<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
  xmlns:a="http://example.org/#">
 
  <rdf:Description rdf:about="http://example.org/blah">
    <a:someProperty rdf:bagID="baz"/>
  </rdf:Description>
</rdf:RDF>
 

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<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
  xmlns:a="http://example.org/#">
 
  <rdf:Description rdf:about="http://example.org/blah">
    <a:someProperty rdf:ID="foo" rdf:bagID="baz"/>
  </rdf:Description>
</rdf:RDF>
 

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  Technology, Institut National de Recherche en Informatique et en
  Automatique, Keio University).
 
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<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
  xmlns:a="http://example.org/#">
 
  <rdf:Description rdf:about="http://example.org/blah">
    <a:someProperty rdf:resource="http://example.org/somewhere" rdf:bagID="baz"/>
  </rdf:Description>
</rdf:RDF>