[mpeg-OTspec] COS and ZHH language system tags

[James Clark]

On Mon, Apr 14, 2014 at 9:37 PM, Levantovsky, Vladimir <
Vladimir.Levantovsky at monotype.com> wrote:

As far as ZHH for Chinese and its description are concerned, this was a
> conscious change that was made in the 3rd edition working draft back in
> February 2013 - this is how the corresponding ISO language tag 'zho' is
> described in the ISO 639 spec.


This argument doesn't make a whole lot of sense to me.  Before this
proposed change, the Chinese-related entries in the language system tags
table were as follows:

Chinese, Hong Kong SAR    ZHH    zho

Chinese Phonetic    ZHP    zho

Chinese Simplified    ZHS    zho

Chinese Traditional    ZHT    zho

Observe that:

- all 4 entries have 'zho' as their ISO language tag
- the final character of the language system tag is mnemonic for the
qualifier applied to "Chinese" (H for Hong Kong, P for Phonetic, S for
Simplified, T for Traditional)

It is important to bear in mind that a "language system", as the term is
used in the standard, is not the same as language; the standard defines a
language system as "a set of typographic conventions for how text in a
given script should be presented".  So here we have 4 different language
systems each specifying a different set of typographic conventions for the
writing a single language, namely Chinese.  Note that the ISO language tags
do not define the precise meaning of the language system: they are no more
than the tags of languages to which the language system might apply.
(Indeed, the ISO language tags column was only added to the OpenType spec
in version 1.6.) It is the first column in the table that constitutes the
definition of the language system tag.

ZHH thus has a clear, well-established meaning as a language system tag: it
refers to the set of typographic conventions used for writing Chinese in
Hong Kong.  ZHH has been in place since OpenType 1.5.

Now, ZHH may not be a very useful tag: I don't know of any typographic
conventions used in Hong Kong beyond those that apply to Chinese in the
traditional script generally.  However, it seems quite extraordinary to me
to suddenly make a major change in the well-established semantics of the
tag.  This should not be done without some really good reason.

Furthermore, this change could create real incompatibilities.  Up to now,
software would only apply the ZHH language system to text identified as
Chinese as used in Hong Kong.  In practical terms, text in HTML with
lang=zh-HK would use the ZHH tag, but text labelled with lang=zh would not.
Similarly, fonts would use ZHH for features that were appropriate in Hong
Kong (which uses traditional characters).  If software now starts to
implement the changed semantics of ZHH in combination with old fonts using
the previous semantics of ZHH, text labelled as generic Chinese will be
displayed using conventions appropriate for Hong Kong (ie traditional
characters), where it had previously been displayed using conventions
appropriate for generic Chinese (probably simplified characters).

James
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