RDF Graph questions

First, a heads up on my action to write a section defining the RDF
graph.
It's progressing, attached (with the usual red and green), still
unfinished, and what is done is quite rough (no consistency in term use,
or capitalization etc. I still need to do my own checking on readability
etc.).


Second a few questions.

1. Are there unattached nodes in an RDF graph?

2. Can any URI ref be a property name or must there be some associated
namespace?

3. For XML literals should I
   - specify that they must be well-balanced XML
   - explicitly permit any unicode string (but only constrain equality
for well-balanced XML)
   - have deliberate vagueness (e.g. talk about a unicode string, and
then only define equality on well-balanced XML and ignore the issue of
whether other strings are permitted or not).


Test cases for 1 & 2.

1:

Is this RDF/XML document

<rdf:RDF><rdf:Description/></rdf:RDF>

equivalent to or different from this one:

<rdf:RDF/>


and/or this one:

<rdf:RDF>
 <rdf:Description rdf:about="http://example.org/"/>
</rdf:RDF>


(the question can't be asked in N-triple)

2:

http://www.w3.org/2000/10/rdf-tests/rdfcore/rdfms-uri-substructure/error
001.nt

whose status is pending

Is this:

a) an error because there is no such RDF graph

or

b) an example of alegal RDF graph that cannot be serialized as RDF/XML

Reading
http://www.w3.org/2000/03/rdf-tracking/#rdfms-uri-substructure

and our resolution is not helpful.



Jeremy