[OpenType] RE: [mpeg-OTspec] Re: Languages tags (Buruchaski & North Slavey)

John Hudson john at tiro.ca
Tue May 24 21:28:51 CEST 2016

On 24/05/16 11:56, Peter Constable wrote:

> With that in mind, SLA could be left as a higher-level category, and the language tag scs could be left as a mapping. But if we really want it to be a higher-level category, then the mapping should list both scs and xsl. Then we'd be left with this:
> Lang system tag: SLA
> Description: Slavey
> ISO 639-3 mappings: scs, xsl
> Lang system tag: SSL
> Description: South Slavey
> ISO 639-3 mappings: xsl
> That suggests a gap that could be filled, as John suggests:
> Lang system tag: SCS
> Description: North Slavey
> ISO 639-3 mappings: scs
> That would work and wouldn't conflict with anything. I wonder if it's overkill: is anybody going to implement fonts that have different glyphs or layout behaviour for SLA versus SSL versus SCS? But I won't object if that's how people want to proceed.

I think it is worthwhile to think about this as a more generalised case, 
rather than thinking about the Slavey languages per se. As Peter notes, 
OTL language system tags were badly under-documented; now they are less 
badly under-documented, but they're not even close to well-documented. 
As with other aspects of OTL, there is no standard implementation 
specification, or even recommendation of best practices.

Something like the structure Peter outlines, above, for Slavey 
languages, looks to me useful in a number of other situations, if it 
were spec'd what client software is supposed to do.

My take on this is that it would be useful to be able to specify 
language *group* systems (by which I mean typographic conventions 
associated with multiple languages, locales, etc.). So I wouldn't expect 
SLA to have distinct behaviour from SSL or SCS, but rather would provide 
a single tag for a single behaviour appropriate to both North and South 
Slavey. If a font maker wanted some distinct behaviour in SSL vs SCS, he 
or she would use those two tags, but otherwise would only need to use SLA.

In order for this to work, there needs to be a defined behaviour for 
software when mapping from ISO 639 language-tagged content to default 
OTL ls tags, such that the software would look first for a one-to-one 
mapping, e.g. scs to SCS for North Slavey, and then for a mapping as 
part of a set, e.g. scs,xsl to SLA for Slavey, and then fall back to dflt.

Am I foolish to assume there is never a situation where a single ISO 
code would map, one-to-one to multiple OTL tags? Any other way this 
could be blown up?



John Hudson
Tiro Typeworks Ltd    www.tiro.com
Salish Sea, BC        tiro at tiro.com

Getting Spiekermann to not like Helvetica is like training
a cat to stay out of water. But I'm impressed that people
know who to ask when they want to ask someone to not like
Helvetica. That's progress. -- David Berlow

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