I agree that having it stated at point of use is useful - and we do that in other cases covered by stability clauses; but we can only state it IF we have the corresponding stability policy.
Mark *— Il meglio è l’inimico del bene —* On Mon, Jul 26, 2010 at 11:06, Asmus Freytag <[email protected]> wrote: > On 7/26/2010 6:55 AM, John Burger wrote: > >> Mark Davis ☕ wrote: >> >> From just a quick scan, it appears that they are currently all contiguous >>> within their respective groups. If we were to impose a stability policy, it >>> would be a constraint on the general_category: we would not assign >>> general_category=decimal_number to any character unless it was part of a >>> contiguous range of 10 such characters with ascending values from 0..9. >>> >> While that is true for the properties, it's not true for the encoding of > character that are *used* as decimal digits. Martin gave the most widely > used counterexample. > > >> >> Whether such a policy makes sense, I'm not clear on why it would be called >> a "stability" policy - the analogy to the existing such policies seems >> strained at best. >> >> There are two parts to this. > > One, and I think this is the more important part, is to have an encoding > policy of not splitting up runs of decimal digits - which would include > reserving a spot for a zero, in case, *over the lifetime of Unicode*, some > script changes their use from numbers 1-9 to decimal digits. > > The other is a guarantee of what it means for a character to have the > decimal digit property. > > My suggestion for handling this, differ a bit from what has been discussed > so far. > > The first I would address by suitable language in the WG2 Principles and > Procedures document. This is where policies on encoding are maintained. > True, these policies do allow exceptions, but exceptions (note Han !) do > exist, and if a similar case of mixed-use character came along, then they > would have to be dealt with accordingly. What the P&P would do is remove the > wrong notion that it is OK to scatter runs of known decimal digits when > encoding new scripts. > > The second I would address not by a stability policy, but by clarity of > definition of the property. Language such as: > > "A character is given the decimal digit property, if and only if, it is > used in a decimal place-value notation and all 10 digits are encoded > in a single unbroken run starting with the digit of value 0, in > ascending > order of magnitude". > > or equivalent would be quite sufficient. That language happens to be a much > clearer statement of the *implicit* definition used in assigning this > property than the language found in UAX#44 or Unicode Section 4.6. > > Having that language where the property is documented is much more useful > and visible than in a stability policy. > > A./ > >
