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Subject: RE: [xri] Normalization and Case Folding
"Implementer's Guide" sounds like it might have overlapping
purposes with the NAC XRI Profile. So, I guess I could be interested in
helping.
Marty.Schleiff@boeing.com;
CISSP From: Drummond Reed [mailto:drummond.reed@cordance.net] Sent: Tuesday, November 08, 2005 10:07 AM To: 'Tan, William'; xri@lists.oasis-open.org Subject: RE: [xri] Normalization and Case Folding Wil, Thanks for pointing
this out. With the XRI Syntax spec frozen, I think we have two options –
publishing this guidance as a best practices recommendation, or including it in
the XRI Implementer's Guide, the new deliverable we have in addition to the
Introduction to XRI document (because the new XRI Resolution draft will have the
non-normative material removed.) We need volunteers to
work on the Implementer's Guide. Do I see any hands up? If you're shy about
responding on the list, you can volunteer over the phone on this Friday's
telecon (8:30AM PT Friday, as usual). =Drummond
From: Tan,
William [mailto:William.Tan@neustar.biz] One issue that recently came up
during implementation is the interaction between NFKC and case folding. For a
small number of characters, case folding is not closed under NFKC. Suppose Q(X)
is a function defined by: Q(X) =
NFKC(CaseFold(X)) The following property is NOT true
for all strings: Q(Q(X)) ==
Q(X) Unicode standard recommends that
additional mapping be performed in order to guarantee the function to be closed
[1]. These mappings are well-defined and are given in the data file http://www.unicode.org/Public/3.2-Update/DerivedNormalizationProps-3.2.0.txt
under the FC_NFKC_Closure mapping. These mappings are also specified in
Stringprep (RFC3454) processing, and are in use by IDNA
Nameprep. For XRI, it means that an
application wishing to accurately test for authority equivalence should apply
the additional mapping when performing case folding. If this is not followed, a
pair of equivalent strings that only differ in case may be falsely treated as
different strings even though case folding has been applied. Perhaps we should
add an additional recommendation to perform the additional mapping when doing
case-less matching of authority in section 2.5 of xri-syntax-V2.0-cd02
“Normalization and Comparison”. wil. [1]
http://www.unicode.org/versions/Unicode4.0.0/ch05.pdf#G21180 |
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