From: Doug Ewell (email@example.com)
Date: Sat Mar 15 2003 - 18:09:53 EST
Chris Jacobs <c dot t dot m dot jacobs at hccnet dot nl> wrote:
> I think it is more important that there be a mechanism to relocate a
> font when you install it.
> Font developers should be free to develop fonts without having to
> decide where in the end-user's pua it is supposed to be.
> My pua, the pua of font developer A, and the pua of font developer B
> should be considered three different spaces, so that there be no
> conflict when developer A and B put different chars on the same code
> And if it works that way I see no end-user problems if a font
> developer has his pua on a place where it not belongs.
The analogy to relocatable program code is intriguing. But as Pim
responded, the whole purpose of data interchange would be defeated if
end users could do this.
Suppose James Ruddy goes ahead and writes his novel in his invented
language, using an invented script I'll call "Ruddian." Suppose he uses
Private Character Editor to create his glyphs, and (for whatever reason)
picks a range beginning at U+E770. Say, for instance, that RUDDIAN
LETTER KA ends up being assigned to U+E773.
If James creates or commissions a font that includes Ruddian characters
in this range, he can make it available to end users so they can read
his novel on the Web.
But when James wants to represent RUDDIAN LETTER KA on his Web page,
he's going to use U+E773. Any other code point will not be KA; it will
be something else (possibly a .notdef glyph). If the end user has
invoked some sort of relocation command to move KA from U+E773 to
somewhere else, he won't be able to read James's text. Only U+E773 will
do. That's why relocatable PUAs won't work; they destroy data
Now, as Chris points out, "developer A" (in this case, the ConScript
Unicode Registry) and "developer B" (William Overington) have already
assigned other characters to U+E773, in their own PUA implementations.
There's already a conflict between A and B, and James (as developer C)
would only be adding to the apparent chaos. And we don't know how many
other individuals and companies might have put something else at U+E773
in various fonts and registries.
That's why it's the PRIVATE use area -- each user gets to choose how the
code space is divided up for his own personal use. (It doesn't mean the
assignments have to be kept secret!) The CSUR assignments can be posted
on the Web, as can William's "Golden Ligature Collection," and other
developers and end users are free to implement those assignments. Or
they can ignore them and create brand-new assignments for the same code
space, as James did in this example. Either approach is totally
Here's an instance of U+E773: 
What do you see?
(a) SOLRESOL SYLLABLE FA
(b) LATIN SMALL LIGATURE F F J
(c) RUDDIAN LETTER KA
(d) a black box, geta mark, or other .notdef glyph
(e) anything else imaginable
Right now, if you see (a), (b), (d), or even (e) you are totally
conformant, and both my sending system and your receiving system are
working correctly. If James makes a Ruddian font available as described
above, then (c) would be OK as well. If your interpretation of U+E773
doesn't match mine, oh well. That's life in the Wild Wild PUA.
So what's the solution? How do we prevent this sort of chaos from
destroying data interchange?
The answer is that any text interchange involving the PUA must depend on
an *agreement* between sender and receiver as to which PUA convention is
being used. In other words, if I send you should have some way of
knowing whether I meant it to be a Solresol syllable, a Golden Ligature,
or something else. There might be an implicit understanding that all
PUA characters on a Web site are encoded according to (e.g.) ConScript,
or it might be explicitly stated at the start of a file or page.
The sample texts on my Web site written in my invented script (see
http://users.adelphia.net/~dewell/udhr-ew.html, for example) are not
exemplary, since they don't say explicitly that the ConScript encoding
is used. I should probably include at least an HTML comment to that
BTW, another problem with "relocatability" is that it would force end
users, who generally don't know squat about the PUA, to make a technical
decision regarding it.
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