From: Otto Stolz (Otto.Stolz@uni-konstanz.de)
Date: Thu Jan 10 2008 - 11:17:40 CST
Hello Murray Sargent,
Jony Rosenne observes:
> See Unicode Standard Annex #9, The Bidirectional Algorithm, clause 3.3.1.
> "The Paragraph Level".
You have written:
> This is the context rule I mentioned. It doesn't handle paragraphs that start
> with a strong character of the opposite direction from the desired paragraph
> direction.
In these cases, the author should insert a strong character of the
desired direction into their plain-text sources, at the beginning of the para-
graphs in question; U+200E and U+200F are precicely made for this purpose,
cf. <http://www.unicode.org/charts/PDF/U2000.pdf>,
and <http://www.unicode.org/versions/Unicode5.0.0/ch16.pdf#G16327>.
If a higher level protocol is used, you’d rather exploit its features.
E. g., in HTML, use the DIR attribute,
cf. <http://www.w3.org/TR/html401/struct/dirlang.html#h-8.2>.
In any case, the author has to express his intent.
Note also that the author has to insert control characters
to tell the bidi algorithm the border between the inented
runs of opposite directionalities, where a sequence of
punctuation marks (or other characters having no stronhg
inherent directionality) spans a region of opposite
directionalities. A common example being a quote of the
other direction: The quotation marks belong to the sur-
rounding text, but the final punctuation of the embedded
quote belongs to the latter, hence needs opposite directionality.
Cf. <http://www.systems.uni-konstanz.de/Otto/Vortrag/Charset/Unicode-Grundlagen.html#UC-Bidi>
for an example (even an amusing one, if you can read
German, and possibly Yiddish.)
The only shortcoming I can see, is that the Bidi algorithm
for plain text applies to only one paragraph. Hence, to specify
RTL direction for a whole chapter or document, the author
must either use a higher level protocol, or take the pains to
mark the direction of every single paragraph that happens to
start with the wrong character. But this is the price to
be payd for setting one’s heart on plain text, I reckon ;-)
Best wishes,
Otto Stolz
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