Peter,
Here's my take on your questions.
> The less clear cases involve b, d and g.
>
> 1) Lower case "b" with a horizontal stroke through the bowl (hereafter
> "b-stroke-bowl") is used in some phonetic traditions for voiced bilabial
> fricative (beta, in IPA). The annotation for U+0180 ("b" with a horizontal
> stroke across the ascender) indicates that one of its intended purposes is
> for phonetic transcription of the same phone. Of course, U+03B2 (beta) also
> has this function and is not unified with 0180, but these are clearly
> distinct characters (e.g. 0180 and 03B2 have other unrelated functions). I
> can't imagine anyone using b-stroke-bowl contrastively with 0180. Thus,
> probably the best option is to treat b-stroke-bowl as a typographic variant
> of 0180.
>
> Any opinions confirming this view or to the contrary?
I agree.
This is what Pullum and Ladusaw called the "Barred B", as opposed to the
Indo-European "Crossed B" (i.e. U+0180):
"By a general convention, barred stop symbols (with a superimposed
hyphen or short dash through the body of the letter) are often used
to represent those fricatives for which the IPA symbols are not used.
The resultant symbols have the advantage of being easy to type on an
unmodified typewriter."
By the way, there is also the "Slashed B", which is another alternative
form for the Barred B, used for the same purpose, but instantiated by
typing b <backspace> / instead of b <backspace> -.
For what it is worth, the founders of Unicode considered these three
forms to be allographs of an abstract barred-b character, so that is
what the current situation is. Trying to separately encode a "Barred B"
distinct from the "Crossed B" would, at this point, constitute an
explicit disunification, rather than simply a discovery of an overlooked
character to encode.
> 2) Next, consider the g. The representative glyph in TUS3.0 for U+01E5
> shows a double-bowl g with a horizontal stroke through both sides of the
> bottom bowl. The annotation indicates that it is used for Skolt Saami.
> Looking at a few fonts, I see some variations: Andale Mono and Code 2000
> have a double-bowl g with a horizontal stroke through *the right side only*
> of the lower bowl; Lucida Sans Unicode and Arial Unicode MS have a
> single-bowl g with a horizontal stroke through the right side only of the
> bowl.
Pullum and Ladusaw show two other glyphic alternatives:
"Barred G" with an IPA style "g" and a horizontal stroke through the bowel.
"Crossed G" with an IPA style "g" and a horizontal stroke through the descender.
>
> Now, what I'm concerned with is a g (single-bowl in all instances I'm
> familiar with) that has a horizontal stroke through both sides of the
> (upper -- only) bowl, used in some phonetic traditions to represent a
> voiced velar fricative (IPA gamma). Any opinions on whether to treat this
> as a new character or as a typographic variant of U+01E5?
All allographs of the same underlying character. The same concepts
and analogies apply here. The "Crossed G" was probably explicitly
formed by analogy from the more-attested Crossed B and Crossed D.
The ones with horizontal strokes through the bowel are all just
variants on what happens when you backspace and put a hyphen across
your "g".
> 3) Finally, the d. Unicode has three upper-case stroked-d characters for
> which the representative glyphs are identical, but which have distinct
> lower-case counterparts (the basis for having three distinct upper-case
> characters). Of the three pairs, two really aren't relevant to this
> discussion. The one relevant pair is U+0110 LATIN CAPITAL LETTER D WITH
> STROKE, and U+0111 LATIN SMALL LETTER D WITH STROKE.
>
> Now, in some phonetic traditions, a "d" with a horizontal stroke through
> the bowl (both sides) is used for a voiced interdental fricative (IPA
> U+00F0). Some phonetic traditions represent this using U+0111.
>
> I've also learned of some African languages that are written with upper and
> lower stroked d; I've seen samples that show some glyph variation: some
> samples show a horizontal stroke that crosses both sides (both upper and
> lower case); other samples show the horizontal stroke on only one side --
> through the stem of the upper case (just like U+00D0, U+0110 and U+0189),
> and through the right side of the bowl of the lower case (not through the
> ascender, as shown in the charts for U+0111).
>
> So, again: any opinions on whether d-stroke-bowl should be unified with
> U+0111 or considered a new character?
Again, all allographs of the same underlying character. And once
again, as for "b", there are, in addition to the "Crossed D" and
"Barred D" allographs, also a "Slashed D" allograph.
There is no need to proliferate distinct encodings for these, whether the
slashes of the "Barred D" forms go all the way across or just partway
across either the lowercase and/or the uppercase forms. Those are just
various typographic attempts to do decent design for the letter forms
based on the concept of having to apply a horizontal stroke to the
"d"/"D" forms.
--Ken
