[webkit-dev] Fwd: Fwd: HTML5 & MathML3 entities

Alexey Proskuryakov ap at webkit.org
Fri Sep 17 16:05:39 PDT 2010

17.09.2010, в 15:32, David Carlisle написал(а):

> adding a canonical decomposition doesn't imply deprecation.
> Depending on which canonical form is chosen, the canonicalisation mapping can go either way, loosely speaking some forms prefer composite characters, some use combining characters in preference (not that combining characters are involved here)

This is not accurate. For singleton decomposition, both NFC and NFD contain the decomposed form. See Unicode 5.2.0 section D113 (full composition exclusion) for details.

> 2329  was deprecated some years after the canonical mapping was added
> because it was realised that that mapping was wrong, but mappings are never changed once added. It became deprecated not when the mapping to 3008 was added; it became deprecated when it was replaced by 27E8
> I described it as a two step process because it happened in two stages.

Because of the above, I don't see how it could happen in two stages. Adding a singleton decomposition logically implies deprecation. And it wasn't until Unicode 5.2 that "deprecated" had a clearly defined meaning anyway.

> It was conformant to unicode 2 yes, the fact that unicode then added a canonical form to 3xxx doesn't make them non conformant, systems don't have to use NFC form and they don't have to use any particular glyph, so for either reason it's perfectly conformant to use a math character for 2329.

Again, both composition and decomposition of U+2329 produces U+3008.

> The point is that there have been documents using those entities as math character names in continuous use since the '80s why should they all be broken? Not to mention the fact that the vast majority of use of those entities in html will also be expecting a mathematical bracket (even if on some systems, with some fonts the character glyph used was actually designed for CJK punctuation).
> In fact where classical ISO usage and HTML usage differed I followed HTML usage in all cases (for all the obvious reasons) even when the HTML definitions make no sense at all (eg asymp) but in this case
> external factors (ie Unicode moving the goalposts) meant that the "new" Uniocde 3.2 character should be used here.

Do these documents use the entities with the same "&...;" notation? MathML didn't exist in the 80's, so what are the documents that actually conflict with HTML, or with compound XHTML documents?

I see that <http://www.w3.org/TR/xml-entity-names/> defines multiple names for the same code points: "lang, langle, LeftAngleBracket and rang, rangle, RightAngleBracket". Do they all really need to have the same meaning?

>>> the only fix the UTC suggest for that is just not using 2329 at all
>>> and use 27E8 instead. Which is what the entity spec recommends.
>> Did they actually suggest to use it for the lang entity in HTML, or
>> did they suggest to use it when a math character is desired?
> xhtml entities have document scope it is not possible for an xhtml+mathml document to have different definitions for html and mathml use, but even for pure html use it is fairly clear that 27e8 is the correct choice.

I wasn't asking about HTML vs. XHTML - both used to define &rang; in the same way. I can re-phrase my question as "Did they actually suggest to use it for the lang entity in (X)HTML, or did they suggest to use it when a math character is desired?"

> rang was never defined to be 3009, it was defined to be 232A  and documented as being a math angle bracket. Unicode have deprecated 232A and suggest that any uses of that be replaced by 27E9 because 232A is effectively unusable as it is subject to an essentially accidental and incorrect normalisation to 3009.
> It would be bizarre in the extreme to redefine rang to be 3009 (is there any evidence of anyone ever having used that entity name and wanting a CJK character?)

I don't think that characterizing what we did in WebKit as bizarre in the extreme is fair. The Unicode spec said that 232A is deprecated in favor of 3009, so it was the only formally correct thing to do.

- WBR, Alexey Proskuryakov

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