text/provenance-notation media type request

Hi Graham and Sandro,

As indicated yesterday, both turtle
http://www.w3.org/TR/turtle/#sec-mediaReg and
sparql
http://www.w3.org/TR/rdf-sparql-query/#mediaType
use the same sentence I adopted for PROV-N:


Encoding considerations:
    The syntax of Turtle is expressed over code points in Unicode
    [UNICODE <http://www.w3.org/TR/turtle/#bib-UNICODE>]. The encoding
    is always UTF-8 [UTF-8 <http://www.w3.org/TR/turtle/#bib-UTF-8>].

Encoding considerations:
    The syntax of the SPARQL Query Language is expressed over code
    points in Unicode [UNICODE
    <http://www.w3.org/TR/rdf-sparql-query/#UNICODE>]. The encoding is
    always UTF-8 [RFC3629 <http://www.w3.org/TR/rdf-sparql-query/#rfc3629>].


There is however an optional parameter: empty for SPARQL and as follows 
for turtle.

Optional parameters:
    |charset| --- this parameter is required when transferring non-ASCII
    data. If present, the value of |charset| is always|UTF-8|.


What is its purpose? do we need this? Sandro, any view?

Regards,
Luc