From: John Hudson (email@example.com)
Date: Thu Aug 23 2007 - 12:53:13 CDT
Ginette Beurton wrote:
> I wonder about the drawbacks generated by the replacement of some of
> the Greek extended characters by the Greek equivalent character when it
> exist, for example : ( u1F71, u1F75, u1F77, u1F79, ...) replaced
> respectively by u03CA, u03AE, U03AF, u03CC, ...
> The question is that, in the Unicode standard, the Greek extended
> characters are declared as equivalent to the Greek ones but the reverse
> is not done.
> For example, u03AF is not declared as an equivalent of u1F71. So the
> relation between the 2 codes is not symmetric. Does that generate any
> drawbacks ?
The three-line equivalency symbol indicates canonical decomposition. This means that, for
instance, U+1F71 canonically decomposes to U+03AC (note, not U+03AF): that the 'alpha with
tonos' character is a fully legitimate way to encode the 'alpha with oxia' character, that
they are identical, and that U+1F71 may be converted to U+03AC during text normalisation.
Note also that U+03AC may itself be decomposed to the base + combining mark sequence
<03B1, 0301>. U+0301 is the generic combining acute mark character.
The only caution I would raise about using U+03AC and other Greek letters with tonos in
place of the equivalent extended letters with oxia is that some font developers,
erroneously in my opinion, make a visual distinction between the tonos mark and the oxia
mark, e.g. by making the tonos mark more vertical. When the monotonic system was
legislated in Greece, there was a brief fad for making strange tonos mark forms such as
triangles, this confused many people and as a result not everyone realises that the tonos
and oxia are, in fact, the same accent.
So using U+03AC instead of U+1F71 may not get the visual result that you want in all
fonts. Of course, performing normalisation decompositions of text may also result in a
change in display with those fonts.
-- Tiro Typeworks www.tiro.com Gulf Islands, BC firstname.lastname@example.org Do not begin to paddle unless you intend always to paddle. - St Jean de BrΓ©beuf, instructions for missionaries, 1637
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