Combining mark vs combining character?
vint at google.com
Wed Jan 5 15:17:37 CET 2011
yes, having general category M seems to encompass both "mark" and
"character" - at least for IDNA2008 purposes.
On Wed, Jan 5, 2011 at 9:07 AM, Simon Josefsson <simon at josefsson.org> wrote:
> Vint Cerf <vint at google.com> writes:
> > Simon,
> > I am pretty sure that the terms "combining mark" and "combining
> > as used in IDNA2008 mean the same thing.
> > neither are permitted as the initial character of a Unicode domain label
> Thanks. And the practical definition of what a combining mark&character
> is that it has a General Category of M as explained in section 3.6 of
> Unicode 5.0 quoted below?
> Note that this is different than having a non-0 Combining Class value.
> > vint
> > On Wed, Jan 5, 2011 at 5:06 AM, Simon Josefsson <simon at josefsson.org>
> >> Hi,
> >> I need a clarification regarding this paragraph in section 220.127.116.11 of
> >> RFC 5891:
> >> The Unicode string MUST NOT begin with a combining mark or combining
> >> character (see The Unicode Standard, Section 2.11 [Unicode] for an
> >> exact definition).
> >> And this in section 5.4:
> >> Putative U-labels with any of the following characteristics MUST be
> >> rejected prior to DNS lookup:
> >> ...
> >> o Labels whose first character is a combining mark (see The Unicode
> >> Standard, Section 2.11 [Unicode]).
> >> The reference to [Unicode] is not normative, which would be a problem
> >> for any implementer.
> >> Reading section 2.11 of Unicode 5.0 discuss "combining character" but
> >> not "combining mark".
> >> There is a section 7.9 in Unicode 5.0 called "Combining Marks".
> >> A section that discuss both Combining Marks and Combining Characters in
> >> the same section is section 3.11 on "Canonical Ordering Behaviour".
> >> There is one section 3.6 on "Combination" that gives the precice
> >> definition of a "Combining character":
> >> Combining character: A character with the General Category of
> >> Combining Mark (M).
> >> Is this the intended definition of Combining character by RFC 5891?
> >> Questions:
> >> 1) Does RFC 5891 refer to "combining mark" and "combining character" as
> >> the same thing?
> >> 2) Is there a significant difference between the requirement in 18.104.22.168
> >> and 5.4? The latter section only mentions "combining mark" and not
> >> "combining character".
> >> 3) What is the precice definition of a "combining mark"?
> >> /Simon
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