Re: ? Reasonable to propose stability policy on numeric type = decimal

From: Mark Davis ☕ (
Date: Mon Jul 26 2010 - 14:13:22 CDT

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    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.


    *— Il meglio è l’inimico del bene —*

    On Mon, Jul 26, 2010 at 11:06, Asmus Freytag <> 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./

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