Re: Missing character: Combining Up Tack Above

From: Asmus Freytag (
Date: Fri Mar 30 2007 - 02:53:16 CST

  • Next message: Kenneth Whistler: "Re: Missing character: Combining Up Tack Above"

    Just because printers in the past grabbed whatever combination worked,
    is not a good guidance as to the suitability of using combinations. If
    the underlying intent is to create a new 'entity' then the requirement
    is to encode that entity. Some entity decompose, but our rules for
    decompositions is not merely that a similar visual effect *can* be
    produced, but that the elements of the decomposition, when combined,
    correctly form the new entity.

    Losing sight of this would be to take a big step backwards, to the days
    when o-slash, for example, was represented with fallback overstrikes
    such as o^H/.

    I will not quibble with Ken's analysis that the new entity is not an Up
    Tack. An I will not quibble with the fact that the entity is a
    modification of a MACRON. I'll take these as read, for the sake of the
    following argument. I remain very much unconvinced that the decoration
    on that macron is correctly represented by a combining vertical line
    above. I can see no convincing evidence in the discussion.

    Because of that, I see as viable alternatives either, the encoding of a
    character to correspond with the entity as a whole, or the encoding of
    the correct modification for the macron. Overall, placement of multiple
    combining marks strikes me as a fragile (except in the context of
    strong, well supported language-based requirements such as for
    Vietnamese, Polytonic Greek and ignoring scripts with so called 'complex
    layout' such as Arabic and similar cases for the moment). Because of
    this, I think that the best user experience might be generated by
    encoding the entity as such.


    On 3/29/2007 4:27 PM, Kenneth Whistler wrote:
    > Philippe Verdy said:
    >> ABOVE).
    > I agree with Philippe that a sequence of existing diacritics (with
    > that being one of the more likely alternatives) would be sufficient
    > for simply being able to represent the text in question digitally.
    > It would give you a unique representation for the text, distinguished
    > from the letters that have only the macrons. With fallback representation,
    > using most existing fonts, you'd be able to distinguish the text
    > just fine, although the vertical line above wouldn't tend to
    > display optimally (connected to the macron). And even that could
    > be fixed by simply creating a font with appropriate ligatures for the
    > diacritic sequences.
    > But...
    >> There's absolutely no evidence that this is a unique diacritic with
    >> distinct semantic.
    > This I completely disagree with. The phonetic guides for the
    > books in question *are* the evidence for a unique diacritic
    > with a distinct semantic. The text even spells out exactly
    > what that "semantic" is for the system in question. That
    > the semantic is not well-founded from either a modern
    > phonological point of view or as a symbol for an English-based
    > pronunciation guide, has no bearing on the distinctness of
    > the written mark as a symbol, as a unit of written text
    > representation, and hence as a valid candidate for being
    > encoded as a character.
    > The fact that a symbol has a graphological history as a diacritic
    > modification of another preexisting symbol does not disqualify
    > the result from being treated as a character in its own right.
    > In this particular instance, I think a case can be made
    > for either approach. Encode the diacritic-modified macron
    > simply with a sequence of the existing encoded macron and
    > another existing mark; or encode a new combining mark for
    > the diacritic-modified macron (and do not canonically
    > decompose the resulting encoded character).
    >> And the second diacritic used on top of the macron is not
    >> really clear.
    > Agreed. I think the printer simply grabbed "apostrophe" punches
    > from a poor quality set of cases for what was already a
    > hacked up set of metal type, where the macrons, breves and
    > such on letters had been created by a similar process in
    > the first place. The overpunched diacritics sometimes look
    > like vertical lines, sometimes tapered vertical lines, sometimes
    > a bit more like acutes, and sometimes more like comma-shaped
    > apostrophes.
    > --Ken

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