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Well, it is not a matter of 'not completely illegal' as if using those code
points is in some way skating on thin ice around the edges of legality of
using Unicode, the specification provides the Private Use Area specifically
so that end users may, if they so choose, use private code point
definitions in order to use special symbols within software packages which
are Unicode compliant: the situation however is that the right to make such
definitions is not exclusive, so although a regular Unicode symbol has a
unique meaning, a Private Use Area definition does not have an absolutely
exclusive meaning except amongst a group of users who choose to accept any
particular meanings as absolute within a certain context.  So, within a
group such as people interested in expressing chess diagrams in Unicode
compatible format within documents specifically about chess, then the code
points could be used, within those documents, as if the definitions were
absolute.  Problems would only occur if a plain text file were processed on
some other computer system set up for, say, ancient Babylonian cuneiform
characters where people interested in that topic might possibly have used
the same code points for representing cuneiform characters.  The chess
diagrams would come out as cuneiform characters.  Likewise, a file intended
to be of cuneiform characters displayed using a chess fount would have
chess pieces here and there in a muddle of some sort.  However, if files
are carefully kept apart and only used in their own contexts, definitions
of code point meanings within the Private Use Area for chess symbols,
cuneiform characters and various other uses is a very useful facility for
electronic typography.  I am aware that the Private Use Area is being used
for cuneiform characters, yet I do not know whether the code points chosen
overlap with those which I have chosen for chess symbols.  Naturally,
anyone else is perfectly entitled to produce their own, different, list of
code point allocations for chess symbols if they wish.  However, if they
wish to use those which I have published, then they are welcome to do so.

I hope that I do not sound too picky about explaining this, but I would
like to avoid any possibility of anyone getting the idea that using such
Private Use Area code points is wrong, as the Private Use Area is a
specifically provided facility for doing such things.

Certainly, some people feel that a better way to produce chess diagrams
would be to use markup of some sort based upon the twelve chess symbols in
regular Unicode rather than use a special fount containing symbols defined
in the Private Use Area.  That is a debatable point, maybe there are
reasons for using both possibilities.  Yet using the Private Use Area of
Unicode in this manner is an entirely proper activity.  I happen to like
the idea of the individual codes for the symbols, perhaps because of having
had the pleasure of having used a metal type chess fount to set chess
diagrams.

In relation to metal chess founts and diagrams, do you happen to know
please as to whether diagrams in old chess books were produced using
woodcuts or engravings of a whole diagram or whether metal chess founts
were used?  In particular, do you happen to know whether the book by
Carrera of 1617 used whole diagrams or a chess fount please?

I am interested in this for its historical aspects.  I have added code
points for symbols for Carrera's Chess into my collection of code points
and am interested to find out more about his book and the way in which it
was produced and also in the way in which D. Carrera represented the
Champion and the Centaur.

William Overington

23 June 2002