Re: What exactly is a "representative glyph"? (referring to U+2591, emoji, and other characters)

From: Jukka K. Korpela (
Date: Sun Jan 04 2009 - 13:50:11 CST

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    (Continuing my previous message, which was sent prematurely.)

    Karl Pentzlin wrote:

    > The printed Unicode 5.0 edition says on p.564 within section 17.1,
    > below the header "Images in the Code Charts and Character Lists":
    > "Each character in these code charts is shown with a representative
    > glyph. A representative glyph is not a prescriptive form of the
    > character, but rather one that enables recognition of the intended
    > character to a knowledgeable user and facilitates lookup of the
    > character in the code charts."

    I think this tries to say that “representative” means roughly the same as
    “typical”, implying some generality in the sense that there are no special
    features, as some fonts have for some characters. I don’t think it really
    says much more than that.

    > Are the following statements true?
    > 1. The representative glyph of U+0323 COMBINING DOT BELOW is a dotted
    > ring on the baseline with a dot beneath of it.

    No, I don’t think it means to say that. If the standard does not describe
    this, it should. The dotted ring is surely not part of the representative
    glyph, or any reasonable glyph. Rather, it indicates the placement of a base
    character to show the typical position of the mark.

    > 2. The representative glyph of U+0020 SPACE is a Latin letter pair
    > "SP" surrounded by a dotted square.

    No, surely not. This too should of course be explained, even though it is
    more or less evident.

    > 3. Representative glyphs are always printable using black color on
    > white background, without using gray shades and/or other colors.

    I don’t think the standard says or means to say that, but it would be a
    natural idea—though the question would arise why one says that.

    > 4. The representative glyph of a character is not necessarily a valid
    > visual representation of the character itself to be used within its
    > plain text use.

    That would not make sense, would it?

    > This especially applies to control codes and space characters which
    > have no glyphic representation by nature,

    For this reason, it should be explained which entries in the charts are not
    representable glyphs but metanotations of a kind.

    > but also for some special
    > cases where the glyphic representation of the character cannot be
    > expressed unambiguously within its block by a glyph printable black
    > on white, e.g. for U+2011 NON_BREAKING HYPHEN or U+2591 LIGHT SHADE
    > (the latter one being a gray shade by nature and by its correct
    > naming).

    For U+2011, the entry in the chart is surely not a representative glyph but
    something that contains it. For U+2591, I would say that the glyph is
    acceptable. Whether it is representative is debatable, so maybe the
    description of “representative” should be augmented with a note about
    restricting to black and white rendering, which is not always optimal for
    all characters.

    > 5. The representative glyph does not denote the character
    > unambiguously (e.g. U+0042/U+0392/U+0412).

    That must be true since characters may well have identical rendering even in
    typical circumstances.

    > 6. The reference glyph of the emoji e-B16 (purple heart) may be a
    > black and white striped heart

    I guess this is the point you are getting at. It looks rather odd to me that
    a character could have color (still less multicolor features) as part of its
    identity, but this seems to be the way Unicode is taking. It may open entire
    new worlds, or cans of worms, or something else.

    To me, something that _needs_ to be in a particular color is an image by
    nature. It can be used inline, inside text, as any image can, but not in
    plain text and it isn’t a character. There is no deep reason why colors
    could not be part of character identity. Until now, it has just seemed to be
    more pragmatic and more useful to treat color indications as belonging to
    other “protocol levels”. I wonder if there is a deep reason, or a good
    reason, or even a serious reason to change this just like that.

     7. If someone provides evidence for a real "STRIPED HEART" symbol,
    > he may propose it, using the same representative glyph as for the
    > purple heart.

    Well, propositions can always be made, and some of them may get rejected at
    first glance. :-)


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