From: Karl Ove Hufthammer (huftis@bigfoot.com)
Date: Mon Apr 22 2002 - 15:07:57 EDT
Andrew Dunbar <hippietrail@yahoo.com> wrote in
news:20020422151928.55414.qmail@web9607.mail.yahoo.com:
> Now no definitions are global or
> official but here's a nice link from Perl6 which does
> a good job of explaining some useful terms:
>
> http://rf.net/~james/perli18n.html#Q2
They have got their definition of 'Coded Character Set' wrong,
though. It's a mapping *from* (the subset of the) integers *to*
characters, not the other way around.
BTW, the Unicode glossary has some useful definitions. Here's how
they define 'glyph':
Glyph. (1) An abstract form that represents one or more glyph
images. (2) A synonym for glyph image. In displaying Unicode
character data, one or more glyphs may be selected to depict a
particular character. These glyphs are selected by a rendering
engine during composition and layout processing. (See also
character.)
Glyph Code. A numeric code that refers to a glyph. Usually, the
glyphs contained in a font are referenced by their glyph code.
Glyph codes may be local to a particular font; that is, a different
font containing the same glyphs may use different codes.
Glyph Identifier. Similar to a glyph code, a glyph identifier is a
label used to refer to a glyph within a font. A font may employ
both local and global glyph identifiers. A collection of global or
universal glyph identifiers is defined by the Association for Font
Information and Interchange (AFII).
Glyph Image. The actual, concrete image of a glyph representation
having been rasterized or otherwise imaged onto some display
surface.
Glyph Metrics. A collection of properties that specify the relative
size and positioning along with other features of a glyph.
Grapheme. (1) A minimally distinctive unit of writing in the
context of a particular writing system. For example, b and d are
distinct graphemes in English writing systems because there exist
distinct words like big and dig. Conversely, a lowercase italiform
letter a and a lowercase Roman letter a are not distinct graphemes
because no word is distinguished on the basis of these two
different forms. A grapheme is for a writing system what a phoneme
is for a phonology. (2) What a user thinks of as a character.
Graphic Character. (1) A character typically associated with a
visible display representation. (See also glyph.) (2) Any character
that is not primarily associated with a control or formatting
function.
-- Karl Ove Hufthammer
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