This is my issue with Round-tripping SPARQL Update and RDF (either Turtle or RDF/XML)
http://www.ietf.org/rfc/rfc3987.txt
Below is cut from ^^
<!--
Duerst & Suignard Standards Track [Page 12]
RFC 3987 Internationalized Resource Identifiers January 2005
conversion using [RFC3490] may be able to better deal with
backwards compatibility issues in case mapping and resolution are
separated, as in the case of using an HTTP proxy.
Note: Internationalized Domain Names may be contained in parts of an
IRI other than the ireg-name part. It is the responsibility of
scheme-specific implementations (if the Internationalized Domain
Name is part of the scheme syntax) or of server-side
implementations (if the Internationalized Domain Name is part of
'iquery') to apply the necessary conversions at the appropriate
point. Example: Trying to validate the Web page at
http://résumé.example.org would lead to an IRI of
http://validator.w3.org/check?uri=http%3A%2F%2Frésumé.
example.org, which would convert to a URI of
http://validator.w3.org/check?uri=http%3A%2F%2Fr%C3%A9sum%C3%A9.
example.org. The server side implementation would be responsible
for making the necessary conversions to be able to retrieve the
Web page.
Systems accepting IRIs MAY also deal with the printable characters in
US-ASCII that are not allowed in URIs, namely "<", ">", '"', space,
"{", "}", "|", "\", "^", and "`", in step 2 above. If these
characters are found but are not converted, then the conversion
SHOULD fail. Please note that the number sign ("#"), the percent
sign ("%"), and the square bracket characters ("[", "]") are not part
of the above list and MUST NOT be converted. Protocols and formats
that have used earlier definitions of IRIs including these characters
MAY require percent-encoding of these characters as a preprocessing
step to extract the actual IRI from a given field. This
preprocessing MAY also be used by applications allowing the user to
enter an IRI.
-->