> My claim was that Unicode is designed to be ISO Latin-1 backwards
> compatible and therefore there should be a Latin-1 backwards
> compatible UTF. This argument has never been defeated by anyone who
I think what we have here is an example of an enthymeme. The missing
premise is stated explicitly here:
Premise A: Unicode is designed to be ISO Latin-1 backwards compatible.
Premise B: Character sets with which Unicode is backwards compatible
require a UTF.
Conclusion: Therefore, [Unicode requires] a Latin-1 backwards compatible
The problem, of course, is that there is no general assent as to the
truth of Premise B. As others have pointed out, Unicode is backwards
compatible with a number of character sets--JIS X 0208, for example.
But it is not self-evidently true or agreed that each such compatible
character set requires a UTF.
If the unstated Premise B is false, then the conclusion itself is false,
and the syllogism is faulty.
I could be more restrictive in the interpretation of what Gunther
means by "backwards compatible"; by reading between the lines, it
appears he doesn't mean cross-mappable or interconvertible, but
instead "encoded so that the entire non-ASCII portion of the
8-bit character set (0x80..0xFF, or 0xA0..0xFF, depending) is
represented in Unicode by a constant offset and data-widening to
16-bits". In this case, there is exactly and only one character
set which meets this requirement: ISO/IEC 8859-1 Latin-1. Calling
this concept "offset compatibility" and restating the syllogism
in this more restrictive form, we have:
Premise A: Unicode is designed so that Latin-1 is offset compatible.
Premise B: Character sets that are offset compatible to Unicode
require a UTF.
Conclusion: Therefore, [Unicode requires] a Latin-1 offset compatible
Even in this form, however, if Premise B is not true, the conclusion
It seems to me that the consensus of the list in this regard is that
Premise B is not true.
This archive was generated by hypermail 2.1.2 : Tue Jul 10 2001 - 17:20:41 EDT