From: unrza3@cd4680fs.rrze.uni-erlangen.de (Markus Kuhn)
Newsgroups: comp.std.internat
Subject: Re: ISO Latin 1 to 7-bit ASCII conversion (final draft!)
Date: 18 Dec 1992 19:14:12 +0100
Organization: Regionales Rechenzentrum Erlangen
Reply-To: mskuhn@immd4.informatik.uni-erlangen.de
NNTP-Posting-Host: cd4680fs.rrze.uni-erlangen.de
Keywords: character sets, ISO 8859-1, terminals, user interface

ojarnef@admin.kth.se, psv@nada.kth.se (Olle Jarnefors) writes:

>> Users should know if the text they read has been converted from the 
>> original Latin 1 text. ...

>Do you have in mind any specific way of visually indicating that
>conversion takes place?  Underlining converted characters?
>Something else?

I had just a good explanation in the documentation and a reminding message
after program start in mind. Extra characters like [(c)] and [x]
again make the replacements longer and destroy the layout even worse.
In some applications, they might be of use, so I'll describe them
as a possible option. If underlining etc. is possible, this would be
more attractive. But powerfull terminals that allow underlining,
bold face etc. often also provide ISO 8859-1 and then we have the
only REAL solution for the whole problem.

BTW: Kermit translates <copyright> to @, which looks similar, but has 
confused me already a lot. But reading USENET articels about transcriptions
using a transcription system is always very confusing.

>> ... This avoids confusion if e.g. someone asks for
>> sending him a 3<fraction 1/2>" disk [3="], which will be displayed
>> after the conversion as 31/2" (= 15.25").

>This particular problem is most easily solved, we suggest, by
>converting the character not to "1/2" but to " 1/2", with an
>initial space character.

This was only one example of a long list of possible problems that
can't be solved by a non 1-1 mapping solution. 1-1 mapping solutions
(e.g. [a:] according to RFC 1345) have the problem, that you need
to transform the possible pure ASCII sequences like [, a, : and ] with an
escape mechanism. This will modify even 7-bit textes and that was not
my intention. I don't want to design an strict encoding, but anything
that makes reading e.g. 8-bit USENET articles easier on old terminals.

>Two of the "high" characters of ISO 8859-1

>160 "A0 '240  NO-BREAK SPACE (NBSP)
>173 "AD '255  SOFT HYPHEN (SHY)

>are not ordinary graphic characters but a sort of hybrid
>characters with both a graphic component and a control
>component.

>For soft hyphen the graphic component is an ordinary hyphen
>glyph.  The functional component is that this glyph should only
>be displayed or printed if the character is at the end of a
>line.  If it is somewhere else in the line, _nothing_ should be
>displayed or printed.

I agree with you completely here, and that is how I would use these
characters if I had to develop a simple text editor with a few
word processing functions. WordStar users will be very familiar with
the SHY and NBSP characters. But the text of ISO 8859-1:1987(E) does
not define the functionality you describe your second and third sentence.

>In the simple, context-insensitive conversion that we are
>dealing with here, SHY should be converted to the empty string,
>since it will occur less often at the end of a line than
>elsewhere.

NO! I and ISO 8859-1 absolutely disagree here with you. SHY has to be
displayed as something similar to a hyphen. If you remove SHYs that are
not at the end of the line or are not followed by space, than this
might be acceptable, but please NEVER remove SHYs at the end of the line.
Even not in the trival context insensitive case that I selected in order
to keep things simple in the hope that many PD developpers will use the system.

>For TABLE 0 we suggest the following changes:

>0b: 173 "AD '255  SOFT HYPHEN (SHY)
>    Now:        "-"
>    Suggestion: ""

No, see above.

>0c: 175 "AF '257  MACRON
>    Now:        SUBST
>    Suggestion: "-"

My first suggestion was " ", but Steve Summit insisted on SUB. Perhaps
"-" is the best solution, especially if MACRON becomes popular for
underlining the previous line.

>0d: 176 "B0 '260  DEGREE SIGN
>    Now:        SUBST
>    Suggestion: "o"

>    This is most often used in numerical data and can, without
>    risk of misunderstanding, be substituted with the lowercase
>    "o", as is often done.

A better suggestion was " ", as 25 C and 23 34' 44'' will still be understood.
I'll change this to " ".

>0e: 188 "BC '274  VULGAR FRACTION ONE QUARTER
>    Now:        "1/4"
>    Suggestion: " 1/4"

One of my goals was to keep the length below 3. There are many other
strings that might cause possible confusion. In a context sensitive
system, this surely would make sense.

>    DIVISION SIGN         
>    Suggestion: "-:"

>    This symbol has the meaning of subtraction in some countries
>    and some application fields.  In addition, division is
>    in some countries normally indicated by "/" rather than ":".
>    We therefore suggest that the conversion should be neutral
>    by trying to approximate the appearance of the symbol,
>    rather than its meaning.  "-:" is better than ":-", since
>    the "-" can't be misinterpreted as a minus on a following
>    number.

I didn't know this, as both DIVISION SIGN and : are used in Germany 
for division. "-:" seems to be quite artificial, so if ":" really causes
much confusion, SUB may be better here. Which countries use ":" for 
substraction?

>1f: 187 "BB '273  RIGHT-POINTING DOUBLE ANGLE QUOTATION MARK
>    Now:        '>'
>    Suggestion: '"'

Why?

>1g: 188 "BC '274  VULGAR FRACTION ONE QUARTER
>    Now:        SUBST
>    Suggestion: "/"

>    By using "/" instead of the general fallback character at
>    least we indicate that the real character was a vulgar
>    fraction.

The important information has been lost, and I would prefer one single
fallback character.

Thank you for your comments. I'll include at least some of them in my text.

BTW: There is a serious bug in the Latin1toASCII function and only one
person has detected it so far ...

Markus

-- 
Markus Kuhn, Computer Science student -=-=- University of Erlangen, Germany
Internet: mskuhn@immd4.informatik.uni-erlangen.de  |  X.500 entry available
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