Marco asked:
> I was peeping in the "Miscellaneous Mathematical Symbols-B" block proposed
> for Unicode 3.2 (http://www.unicode.org/charts/draftunicode32/U32-2980.pdf),
> when I noticed that many of those character could have been composed using
> an existing base character and an existing non spacing mark.
>
> But they don't have any compatibility decomposition. And this is also true
> for all existing symbols that could be composed with diacritics. What is the
> rationale for this choice?
Consistency with the existing list. When math symbols in Unicode were
originally run through the decomposition wringer for Unicode 2.0 (when
the UTC made its first determined effort to nail all this down, to match
the formal introduction of decomposition [section 3.6 Decomposition, page
3-6 .. 3-7, TUS, Version 2.0], the only systematic pattern which was
abstracted off was the use of the negation slash over various operators.
All other instances of things that *could* be decomposed in theory
were viewed as too marginal and mostly unhelpful to do. For instance,
decomposing off the circle around the circled operators, U+2295..U+229D
would have just made the characters *more* difficult to deal with in
text. Conceptually, they are just unitary symbols.
> For instance:
>
> - 29B1..29B4 (empty sets) could be composed using various diacritics (0305,
> 030A, 20D6, 20D7);
The basic empty set symbol U+2205 is not decomposed, so why should the
new ones be?
>
> - 29B5..29C3 (circle symbols) could be composed using 20DD (COMBINING
> ENCLOSING CIRCLE)
Same consistency argument. Cf. 2295..229D.
>
> - 29C4..29C8 (square symbols) could be composed using 20DE (COMBINING
> ENCLOSING SQUARE)
Same consistency argument. Cf. 229E..22A1.
>
> - 29CC (triangle symbols) could be composed using 20E4 (a new combining
> encoding triangle, also in 3.2:
> http://www.unicode.org/charts/draftunicode32/U32-20D0.pdf)
No advantage, and would be inconsistent with the treatment of the circled
and squared operators.
--Ken
This archive was generated by hypermail 2.1.2 : Fri Jul 06 2001 - 00:17:18 EDT