L2/07-392

Date: Wed, 17 Oct 2007 21:29:13 +0100
From: Michael Everson
Subject: Irish comments on L2/07-340 "OGHAM SPACE MARK
		shouldn't be whitespace"

Mark Davis' suggestion that U+1680 OGHAM SPACE
MARK is not white space seems to be based on a
misunderstanding of the use of the character. His
assertion "Users of the UCD expect that
whitespace characters are, well, white space --
that is, that they do not have visible glyph in
normal usage" is, in our view, incorrect. Users
of the **Ogham script** do, in fact, expect this
character to act as a white space. Other users of
the UCD are unlikely to have expectations about
the Ogham script at all.

An Ogham font may have a stemline. The stemline
represents the edge of a stone in Ogham
inscriptions, or the conventional written
stemline written in ink in manuscripts. However,
an Ogham font may also have **no** stemline.

The annex describing font design in Irish
Standard 424:1999 states this clearly:

=====
1. Cuid roghnach den chló is ea an líne láir. Is gnách
líne láir a úsáid in Ogham na lámhscríbhinní agus sa
chlódóireacht, ach ní gá sin. Nuair nach bhfuil líne
láir in úsáid, ba cheart charachtar COMHARTHA OGHAIM
SPÁS a dhearadh ar an ngnáthleithead, ach é a fhágaint
bán ar aon dul le SPÁS.

1. The centre line is optional. In printing and
in manuscript Ogham it is conventional to design
with a centre line, but this is not necessary. In
implementations without the centre line, the
character OGHAM SPACE MARK should be given its
conventional width, and simply left blank like
SPACE.
=====

See http://www.evertype.com/standards/iso10646/pdf/is434.pdf

The OGHAM SPACE MARK **may** have a visible
glyph. But it also **may not** have a visible
glyph. And when it does have a visible glyph,
that glyph is not actually part of the letter,
any more than the stemline in OGHAM LETTER FEARN
is a part of the letter. OGHAM LETTER FEARN is
three strokes to the right of the edge of the
stone. That edge may be drawn in a font (in which
case OGHAM SPACE MARK should have a visible
glyph) or it may not be (in which case OGHAM
SPACE MARK should not have a visible glyph). The
stemline is more an indication of layout; it is
not an integral part of the letter.

It is incorrect to claim that the conventional
representation of OGHAM SPACE MARK is similar to
ETHIOPIC WORDSPACE. ETHIOPIC WORDSPACE is a
conventional set of dots used to separate words.
This is not what OGHAM SPACE MARK is.

The definition of White Space given here:
http://www.unicode.org/Public/UNIDATA/UCD.html#White_Space
is:

'Those separator characters and control characters which should be treated by
programming languages as "white space" for the purpose of parsing elements.'

There is no statement that it actually has to be
"white space" on the page. If you imagine writing
a program to search for Ogham strings, then
U+1680 would behave exactly as U+0020 in
searching Latin-script text, and indeed in
UnicodeData.txt they have identical properties.
Mark Davis' suggestion seems to be using a
narrower definition, implied by the name "White
Space".

According to UAX14 on line breaking:

"The Ogham space mark is rendered visibly between
words but should be elided at the end of a line."

This is also the correct behaviour.

The Irish National Body requests that the Unicode
Technical Committee to make **NO CHANGE** to the
properties of the OGHAM SPACE MARK. It is
correctly specified at present. Its specification
at present meets the need of the user community,
and we oppose the proposed change.
--
Michael Everson
Convener
NSAI/ICTSCC/SC4 "Codes, Character Sets, and Internationalization"