Another rule which isn't written into Unicode but I like (don't know if Everson
and Whistler and others will), is the font clarity rule. Given a font minus one
character, I should be able to predict what that character will look like. If I
have a S�tterlin font or a Fraktur font, I know what the � will look like. It may
look nothing like it would in Times New Roman, but it will look right for that
font. If there are two seriously different glyphic choices for a character in
one font style, then you have inappropriately unified the two characters.
I think this is a good rule of thumb in several respects. In essence, there is a difference between using two different shapes for the same symbol and the use of two different symbols for the same concept.
Both cases result in the use of two different shapes for the same concept, but the two cases are very different nevertheless.
In case of the specific symbols that started this thread:
I can corroborate Markus' input that these symbols are part of an alternate
and probably originally European convention for denoting the two concepts.
I remember that the rotated E and A symbols looked strange to me, when I
first saw them. This notational difference is *not* something that can or should be
addressed by a font difference. I don't have access to a relevant text to check
whether the two symbols differ from the ones used for AND and OR. If they do not,
that would be an unfortunate overloading of symbols, but not grounds to code
new characters. If they do differ, we are missing some characters.
On the web, the use of rotated A and E are apparently universal - at least I've not
been able to find any examples of the other notation.
A./
PS: I'll forward this issue to our math symbol experts
